Cationic polyamines for treatment of viruses

ABSTRACT

Antiviral cationic polyamines were prepared by modifying polyethylenimines with N-acylating agents that introduce a side chain comprising one or more carbons and at least one alcohol hydroxy group. The cationic polyamines can have a linear or branched polyethylenimine backbone structure. Preferably, the cationic polyamines comprise pendant monosaccharide groups, which can be introduced via a cyclic carbonate comprising a pendant protected monosaccharide (e.g., mannose) group. The cationic polyamines can be active and selective against a broad spectrum of viruses at low concentrations, and are generally non-toxic.

BACKGROUND

The invention relates to cationic polyamines for treatment of viralinfections and methods thereof, and more specifically, to cationicmodified polyethylenimines for anti-viral applications.

Treatment of viral infections continues to be elusive owing to thevariance in virus structure (RNA, DNA, enveloped and non-envelopedviruses) together with their ability to rapidly mutate and acquireresistance. Viral diseases continue to be one of the leading causes ofmorbidity and mortality since ancient times. In recent years, viralinfections have emerged as an eminent global public health problemmainly because of a rapid increase in human population, aging, climatechange, and medical treatments that suppress the immune system,including irradiation therapy, anti-cancer chemotherapy and organtransplantation. For example, the worldwide outbreak of severe acuterespiratory syndrome (SARS) in 2003, dengue fever, and bird flu (e.g.,H1N1) outbreaks in Asia over the last two decades have imposed anenormous economic burden. More recently, several new viral pathogenslike Nipah virus, Chikungunya virus (CHIKV), and mutated pandemic birdflu virus (e.g., H7N9) have been found in the human population.Consequently, significant effort has been directed to develop vaccinesand anti-viral drugs to control and eradicate viral infections. However,the rapid mutation of viruses (especially flu virus), due to inherentgenomic instability, makes vaccinations inefficient. Moreover, for manyviral infections (e.g., dengue and Chikungunya viruses) there are noclinical drugs available. Since there are so many types and subtypes ofpathogenic viruses that easily mutate to form drug-resistant strains,controlling them individually has not been possible.

Viruses can be classified into DNA and RNA viruses according to thegenes they hold, as well as enveloped and non-enveloped viruses. Thisshows the complexity of the problem in attempting to design a generalanti-viral agent. Most emerging and re-emerging viruses belong to theRNA type, including flavivirus family (e.g., dengue virus, or DENV),influenza, CHIKV, Enterovirus 71 (EV 71), and SARS Co-V. Many of theseviruses exploit an endosomal pathway to infect cells. The low pH of theendosome allows introduction of viral genomes into cytoplasm.Furthermore, a number of enveloped viruses utilize anionicphosphatidylserine (PS)/TIM (T cell/transmembrane, immunoglobulin, andmucin) receptor binding and/or the apoptotic cell clearance pathway forentry to cells. This suggests that masking TIM receptors may provide newavenues for controlling viral infection.

Due to the existence of cationic and anionic regions on the viralsurface, charged polymers potentially provide a means of exploitingelectrostatic interactions to inhibit viral infections. However,attempts to prevent viral infections using anionic polymers (e.g.,sulfated polysaccharides such as dextran, xylofuranan, ribofuranan andcurdlan) to bind with cationic charges on the viral surface met limitedsuccess.

Heparin, extracted from animals, has strong activity against denguevirus, but has limited utility since it is an anti-coagulant.

Cationic polymers including cationic acrylate polymers,polyethylenimines and cationic poly(phenylene ethylene) polymers canalso potentially interact with anionic groups of the viral surface bynon-specific electrostatic interactions.

Polyethylenimines (PEIs) are polyamines that are commercially availablein a broad range of molecular weights. The PEIs are formed as eitherlinear (LPEI) or branched (BPEI) macromolecules. PEIs have found manyapplications in products, such as detergents, adhesives, water treatmentagents, and cosmetics. Due to their ability to enter a cell through thecell membrane, PEIs have been utilized as drug carriers in biomedicalapplications. Polycationic PEIs can mediate gene transfer into mammaliancells in vitro and in vivo as a complex with DNA. However, cationicpolymers such as linear polyethylenimine (PEI) exhibit high non-specificcytotoxicity towards mammalian cells and induce hemolysis. Moreover, thelinear PEI is less water soluble than branched PEI.

A number of viral infections are pH-dependent, where low pH in theendosome is required for replication. Recently, niclosamide, an FDAapproved anti-helminthic compound, was reported to prevent infections ofpH-dependent viruses by neutralizing the endosomal pH. However, itshighest selectivity was only ˜24 against influenza virus (PR8) and humanrhinovirus (HRV14). Ammonium chloride and chloroquine having pHneutralization ability were also reported to prevent viral infections,but they are highly toxic, limiting clinical applications.

An ongoing need exists for broad spectrum anti-viral agents that arenon-hemolytic and that provide general and safe strategies to preventviral infections. Anti-viral macromolecules with distinctive functionalgroups are needed to specifically bind to viral surface proteins as wellas compete with viruses for immune cell/target cell binding to preventinfection.

SUMMARY

Accordingly, a method is disclosed, comprising:

treating a virus with a cationic polyamine, thereby forming a treatedvirus comprising the cationic polyamine bound by non-covalentinteractions to the virus;

wherein:

i) the treated virus is less capable of entering a living mammalian celland/or undergoing replication within a living mammalian cell compared tothe untreated virus,

ii) the cationic polyamine comprises:

-   -   a plurality of non-charged N-acylated ethylenimine units of        formula (1):

wherein each K′ comprises at least one carbon and at least one alcoholhydroxyl group, and

-   -   a plurality of positive-charged secondary ethylenimine units of        formula (3a):

wherein the starred bond of the nitrogen is linked to a carbon and X^(⊖)is a negative-charged counterion bound by non-covalent association withthe positive charged nitrogen, and

iii) the cationic polyamine comprises the N-acylated ethylenimine unitsand the secondary ethylenimine units arranged in a random distributionand linked covalently head-to-tail, wherein nitrogen 1 of a givenethylenimine unit is linked to carbon 3 of a different ethylenimineunit.

Also disclosed is a method comprising:

treating a living mammalian cell with a cationic polyamine, therebyforming a treated cell comprising the cationic polyamine and the cellbound by non-covalent interactions;

wherein:

i) the treated cell has more resistance to a virus entering the treatedcell and/or replicating within the treated cell compared to theuntreated cell,

ii) the cationic polyamine comprises:

a plurality of non-charged N-acylated ethylenimine units of formula (1):

wherein each K′ comprises at least one carbon and at least one alcoholhydroxyl group, and

-   -   a plurality of positive-charged secondary ethylenimine units of        formula (3a):

wherein the starred bond of the nitrogen is linked to a carbon, andX^(⊖) is a negative-charged counterion bound by non-covalent associationwith the positive charged nitrogen, and

iii) the cationic polyamine comprises the N-acylated ethylenimine unitsand the secondary ethylenimine units arranged in a random distributionand linked covalently head-to-tail, wherein nitrogen 1 of a givenethylenimine unit is linked to carbon 3 of a different ethylenimineunit.

Another method is disclosed, comprising:

administering to a patient infected with a virus a therapeuticallyeffective amount of a cationic polyamine, thereby inhibiting and/orpreventing replication of the virus;

wherein:

i) the cationic polyamine comprises:

-   -   a plurality of non-charged N-acylated ethylenimine units of        formula (1):

wherein each K′ comprises at least one carbon and at least one alcoholhydroxyl group, and

-   -   a plurality of positive-charged secondary ethylenimine units of        formula (3a):

wherein the starred bond of the nitrogen is linked to a carbon, andX^(⊖) is a negative-charged counterion bound by non-covalent associationwith the positive charged nitrogen, and

ii) the cationic polyamine comprises the N-acylated ethylenimine unitsand the secondary ethylenimine units arranged in a random distributionand linked covalently head-to-tail, wherein nitrogen 1 of a givenethylenimine unit is linked to carbon 3 of a different ethylenimineunit.

The above-described and other features and advantages of the presentinvention will be appreciated and understood by those skilled in the artfrom the following detailed description, drawings, and appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a ¹H NMR spectrum of cationic polyamine B3 in CDCl₃.

FIG. 2A is a ¹H NMR spectrum of the precursor to cationic polyamine B11taken in MeOD before hydrogenolysis. The branched polyethyleniminestructure is a simplified rendition for assigning NMR peaks.

FIG. 2B is a ¹H NMR spectra taken in D₂O of cationic polyamine B11 afterhydrogenolysis and acidification. The branched polyethyleniminestructure is a simplified rendition for assigning NMR peaks.

FIG. 3 is a graph showing the ability of cationic polyamine B3 toprevent infection of human primary peripheral blood mononuclear cellswith the DENV-2 virus. After virus infection, the peak shifts to ahigher PE-A (phycoerythrin (PE)-conjugated anti-mouse IgG). The peaksfor the samples obtained from treatment with B3 at 2 or 10 mg/L do notshift, but rather almost overlap with the peak for the control samplewithout virus infection, indicating that B3 treatment effectivelyprevents human primary peripheral blood mononuclear cells from DENV-2infection.

FIG. 4 is a graph showing the ability of cationic polyamine B3 toprevent infection of macrophages with the DENV-2 virus. After virusinfection, the peak is shifted to a slightly higher PE-A. The peaks forthe samples obtained from B3 treatment at 2 or 10 mg/L do not shift, butrather almost overlap with the peak for the control sample without virusinfection, indicating that B3 treatment effectively prevents macrophagesfrom DENV-2 infection.

FIG. 5 is a bar graph comparing CHIKV (Chikungunya virus) infectionrates of 293T cells expressing the TIM-1 receptor or TIM-3 receptorcompared to empty vector 293T cells that do not express the TIM-1receptor or the TIM-3 receptor (labeled “empty”). The presence of theTIM-1 receptor or TIM-3 receptor enhances CHIKV infection.

FIG. 6 is a bar graph showing the effect of cationic polyamine B3 inpreventing CHIKV infection of empty vector 293T cells (i.e., that do notexpress the TIM-1 or TIM3 receptor). The EC50 was 0.21 mg/L.

FIG. 7 is a bar graph showing the effect of cationic polyamine B3 inpreventing CHIKV infection in the 293T cells that express the TIM-1receptor. The EC50 was 1.26 mg/L and the selectivity index (CC50/EC50)was >794.

FIG. 8 is a bar graph showing the effect of cationic polyamine B3 inpreventing CHIKV infection in the 293T cells that express the TIM-3receptor. The EC50 was 0.68 mg/L and the selectivity index (CC50/EC50)was >1471.

FIG. 9 is a bar graph showing the effect of cationic polyamine B3 inpreventing DENV-2 infection of A549 cells that naturally express TIM-1receptor. The EC50 was 6.8 mg/L, the CC50 was >1000 mg/L, and theselectivity index was >147.

FIG. 10 is a bar graph comparing the luciferase activity of the cellswith cationic polyamine B3, without B3 (labeled DMSO), and with a potentanti-viral adenosine nucleoside analogue NITD008(2R,3R,4R,5R)-2-(4-aminopyrrolo[2,3-d]pyrimidin-7-yl)-3-ethynyl-5-(hydroxy-methyl)oxolane-3,4-diol.This finding demonstrated that anti-viral polymer B3 did not function ata late stage of the DENV-2 cell entry and replication cycle.

FIG. 11 is a set of graphs showing the effect of time of addition ofcationic polyamine B3 (and heparin) on the inhibition of DENV-2 inLLC-MK2 cells. For time=−1.5 hours, the virus and B3 were added togetherto the cells at 4° C. For all other times, B3 was added after the virusand cells were incubated at 4° C. for 1.5 hours and warmed to 37° C. Theresults show B3 was effective in preventing viral infection when addedduring the viral attachment step or early post-attachment step (0-1hours), but was not effective thereafter.

FIG. 12 is a bar graph showing the effect of combining the DENV-2 virusand cationic polyamine B3 one hour at 4° C. before the addition ofLLC-MK2 cells. A 40% reduction in virus titer was obtained, indicatingB3 binding to the virus inhibited viral infection.

FIG. 13 is a bar graph showing the effect of pretreating LLC-MK2 cellswith cationic polyamine B3 for 15 minutes to 2 hours at 37° C. beforethe addition of DENV-2 virus. The EC50 value was 8.7 mg/L, indicating B3binding to the cell membrane was a factor in inhibiting infection byDENV-2 virus.

FIG. 14 is a set of photomicrographs and corresponding procedurediagrams showing the effect of cationic polyamine B3 and heparin onvirus-infected cell fusion. Aedes albopictus C6/36 cells were treatedwith DENV-2 virus. The anti-viral agent was added at 4° C. (imageslabeled “4° C.+”) or at 28° C. (images labeled “4° C.-”). The sampleslabeled “Medium” contained only cells and virus (no anti-viral agent).The samples labeled “Mock” contained only cells (no virus or anti-viralagent). No fused cells were found in the samples containing B3.

FIG. 15 is a two dimensional structure of a model macromolecule of modelbranched PEI built using Marvin Sketch software. The model branched BPEIwas not intended to represent the complete structure of the branched PEIused in the examples.

FIG. 16 is a 3-dimensional computer drawing using MVD (Molegro VirtualDocker) software of the DENV-2 E protein (envelope protein), withhighlighted speckled areas representing 4 poses of the model branchedPEI bound with equal binding energy in 4 docking grids.

FIG. 17 is a computer drawing using MVD software showing the 8 aminoacid residues of the DENV-2 E protein that form hydrogen bonds with amodel cationic polyamine B3 structure: Thr 268(A), Gly 266(A), Ala267(A), Thr 70(B), Thr 115(B), Gln 248(B), Leu 277(A), and Asp 154(A).The model cationic polyamine B3 structure was not intended to representthe complete structure of B3 prepared in the examples. The model B3material had 3 mannose groups.

FIG. 18 is a 3-dimensional computer drawing using MVD software of thefavored binding interaction of the model cationic polyamine B3 with theDENV-2 E protein.

FIG. 19 is a computer drawing using MVD software showing the 7 aminoacid groups of EV 71 VP1 protein that form hydrogen bonds with the modelcationic polyamine B3: Gln 269, Arg 267, Glu 124, Asn 228, Ser 275, Ala224, and Gly 223.

FIG. 20 is a 3-dimensional computer drawing using MVD software showingthe favored binding interaction of the model cationic polyamine B3 withthe EV 71 VP1 protein.

FIG. 21 is a computer drawing using MVD software showing the 7 aminoacid groups of HSV-1 GD protein that form hydrogen bonds with the modelcationic polyamine B3: Asp 13, Asn 15, Arg 18, Leu 22, Val 24, Gln 27,Ser 8.

FIG. 22 is a 3-dimensional computer drawing using MVD software showingthe most favored binding interaction of the model cationic polyamine B3with the HSV-1 GD protein.

FIG. 23 is a computer drawing using MVD software showing the 7 aminoacid residues of DENV-3 E protein that form hydrogen bonds with themodel cationic polyamine B3: Thr 155(B), Lys 47(B), Thr 274(B), Ser271(B), Asn 8(B), and Asp 98(A), His 27(B),

FIG. 24 is a 3-dimensional computer drawing using MVD software of 5cavities in the DENV-3 E protein.

FIG. 25 is a 3-dimensional computer drawing using MVD software showingthe most favored binding interaction of the model cationic polyamine B3with the DENV-3 E protein.

FIG. 26 is a computer drawing using MVD software showing the 7 aminoacid residues of the CHIKV E1 protein that interact by hydrogen bondingwith the model cationic polyamine B3: Gln 373, Gln 368, Thr 17, Gly 12,Glu 32, Thr 338, and His 394.

FIG. 27 is a 3-dimensional computer drawing using MVD software of themost favored binding interaction of the model cationic polyamine B3 withthe CHIKV E1 protein.

FIG. 28 is a computer drawing using MVD software showing the 4 aminoacid residues of influenza virus HA protein that form hydrogen bondswith the model cationic polyamine B3: Arg 285, Ser 282, Ser 130, and Phe415.

FIG. 29 is a 3-dimensional computer drawing using MVD software of the 4cavities in the HA protein.

FIG. 30 is a 3-dimensional computer drawing using MVD software showingthe most favored binding of the model cationic polyamine B3 to the HAprotein.

FIG. 31 is a computer drawing using MVD software showing the 9 aminoacid residues of HSV-2 GD protein that form hydrogen bonds with themodel cationic polyamine B3: Asp 139, Arg 222, Ser 140, Asp 26, Asn 227,Thr 230, Lys 237, Val 24, and Gln 27.

FIG. 32 is a 3-dimensional computer drawing using MVD software of 4cavities in the GD protein.

FIG. 33 is a 3-dimensional computer drawing using MVD software showingthe most favored binding interaction of the model cationic polyamine B3to the GD protein.

FIG. 34 is a computer drawing using MVD software showing the 8 aminoacid residues of the TIM-1 protein that form hydrogen bonds with themodel cationic polyamine B3: Lys 102(B), Ser 3(B), Thr 20(A), Thr 20(B),Ser 22(A), Gln 101 (A), Asp 100(A), and Glu 6(B).

FIG. 35 is a 3-dimensional computer drawing using MVD software showingthe most favored binding interaction of the model cationic polyamine B3to the TIM-1 protein.

FIG. 36 is a computer drawing using MVD software showing the 5 aminoacid residues of TIM-3 protein that form hydrogen bonds with the modelcationic polyamine B3: Glu 106(A), Cys 39(A), Lys 103(A), Ser 20(A), andTyr 7(A).

FIG. 37 is a 3-dimensional computer drawing using MVD software showingthe most favored binding of the model cationic polyamine B3 to TIM-3.

FIG. 38 is a computer drawing using MVD software showing the 3 aminoacid residues of the DENV-3 E protein that form hydrogen bonds with themodel cationic polyamine B3 structure: Glu 13(A), Ala 35(A), and Phe335(A).

FIG. 39 is a 3-dimensional computer drawing using MVD software showingthe most favored binding interaction of the model cationic polyamine B3to the DENV-3 E protein.

FIG. 40 is a computer drawing using MVD software showing the 5 aminoacid residues of the Influenza HA protein that form hydrogen bonds withthe model cationic polyamine B2: Arg 285, Glu 430, Ser 282, Ile 283, andAsp 287. The model B2 material had 2 mannose groups.

FIG. 41 is a 3-dimensional computer drawing using MVD software showingthe most favored binding of the model cationic polyamine B2 to theInfluenza HA protein.

DETAILED DESCRIPTION

Disclosed are methods of preventing, treating, and/or inhibiting a virusfrom entering and/or replicating in a mammalian cell. The methodsutilize modified polyethylenimines (PEIs), referred to herein ascationic polyamines. The cationic polyamines comprise side chains havingthe general structure *—C(═O)—K′ linked to respective backbonenitrogens, wherein K′ comprises at least one carbon and at least onealcohol group. The cationic polyamines can comprise 1 to about 70*—C(═O)—K′ side chain groups linked to the primary and secondary aminegroups of the PEI. Between 0% and about 70%, preferably about 20% toabout 40%, of the total number of amine groups (i.e., primary, secondaryand tertiary amine groups) of the PEI comprise a K′ group. More than 0%and up to 100% of any remaining non-modified primary, secondary, andtertiary amine groups of the cationic polyamine are present inprotonated form as an ammonium salt. In an embodiment, each K′ groupcomprises a monosaccharide moiety (sugar moiety).

The cationic polyamines can compete with immune cells as well as targetcells in binding with virus envelope proteins (E proteins), therebyimpeding entry of the virus into a mammalian cell, alleviating stress onthe immune system, and mitigating side effects due to immunodeficiency.Molecular docking computations reveal an unexpected and generallyspecific interaction of the cationic polyamines with viral surfaceproteins. Virus binding assays demonstrated significant reduction ininfection after incubating virus with a cationic polyamine. Thegenerality of this dynamic hydrogen-bonding specific interactionprovides broad spectrum antiviral activity that appears to be immune tomutations, thereby mitigating and/or preventing development of viralresistance.

The cationic polyamines can also disrupt viral entry into a mammaliancell by binding to surface proteins and other molecules such as heparansulfate proteoglycan of the cells. For example, the cationic polyaminescan bind to TIM (T-cell immunoglobulin and mucin) receptor proteins,thereby inhibiting viruses that target TIM receptors of mammalian cells.The treated cells can have EC50 values (i.e., effective concentration ofthe cationic polyamine that inhibits 50% of the cells from viralinfection) in a range of about 2.7 to about 6.8 mg/L, depending on thetype of TIM receptor.

The pH buffering capacity of the cationic polyamines can also inhibitacid-driven endosomal release of the virus, thereby impeding viralreplication.

The cationic polyamines can inhibit one or more viruses. Representativeviruses include dengue virus (e.g., DENV-1, DENV-2, DENV-3, and/orDENV-4), influenza virus (A/H3N2), CHIKV (Chikungunya virus), SARS Co-V(SARS corona virus), EV 71 (Enterovirus 71), and herpes simplex viruses(e.g., HSV-1 and HSV-2). In some instances, viral activity waseffectively inhibited at cationic polyamine concentration as low as0.012 mg/L, with high selectivity over mammalian cells. The cationicpolyamines can be non-cytotoxic and non-hemolytic to mammalian cells atthe effective concentration against the virus.

Cationic Polyamines

The cationic polyamines comprise at least one polymer branch having apolymer backbone that comprises a plurality of repeat units referred toherein as ethylenimine units. Each of the ethylenimine units has 1backbone nitrogen and 2 backbone carbons arranged as follows:

Herein, starred bonds represent attachment points, not methyl groups. Itshould be understood that the nitrogen labeled 1 is trivalent and eachcarbon is tetravalent. Other substituents on the carbons and nitrogenare not shown in the above structure. The nitrogen labeled 1 representsthe head of a given ethylenimine unit, and the carbon labeled 3represents the tail of a given ethylenimine unit. Adjacent ethylenimineunits are covalently linked head to tail (the starred bond of nitrogen 1of a given ethylenimine unit is linked to carbon 3 of an adjacentethylenimine unit).

The cationic polyamines can be effective anti-viral agents withouthaving a backbone nitrogen in the form of a quaternary ammonium salt.Herein, a quaternary ammonium salt comprises a positive-charged nitrogenthat is covalently linked only to carbons (e.g., 4 carbons) and isnon-covalently associated with a negative-charged counterion X^(⊖). Thepositive charged nitrogen of a quaternary ammonium salt is notcovalently bound to any hydrogen. In an embodiment, the cationicpolyamine structure excludes any backbone nitrogen in the form ofquaternary ammonium salt.

The cationic polyamines comprise one or more polymer chains (branches)comprising ethylenimine units. A linear cationic polyamine comprises i)one branch comprising a plurality of ethylenimine units and ii) twopolymer chain end groups (also referred to as peripheral end groups, ordangling end groups). A branched cationic polyamine comprises two ormore intersecting branches comprising ethylenimine units, and three ormore peripheral end groups.

Scheme 1 illustrates examples of the alternating arrangement of backbonecarbon pairs and backbone nitrogens of the ethylenimine units of alinear cationic polyamine and of a branched cationic polyamine havingtwo branches. The *—C—C—N—* unit enclosed in parentheses represents anethylenimine unit. End groups, charges, counterions and substituents ofthe backbone carbons and nitrogens are not shown.

As shown above, adjacent *—C—C—N—* units are linked head to tail (i.e.,nitrogen 1 of one ethylenimine unit is linked to carbon 3 of an adjacentethylenimine unit).

Backbone primary, secondary, and tertiary amine nitrogens of thecationic polyamine can be present as ammonium salts of a protic acid(i.e., primary ammonium salt, secondary ammonium salt, or tertiaryammonium salt). A primary ammonium salt comprises a positive-chargednitrogen covalently linked to 1 carbon and 3 hydrogens, andnon-covalently associated with a negative-charged counterion. Asecondary ammonium salt comprises a positive-charged nitrogen covalentlylinked to 2 carbons and 2 hydrogens, and non-covalently associated witha negative-charged counterion. A tertiary ammonium salt comprises apositive-charged nitrogen covalently linked to 3 carbons and 1 hydrogen,and non-covalently associated with a negative-charged counterion.

The cationic polyamines comprise at least one non-charged N-acylatedethylenimine units of formula (1):

wherein each K′ is a group comprising at least one carbon and at leastone alcohol hydroxy group.

The cationic polyamines further comprise a plurality of ethylenimineunits independently selected from the group consisting of:

i) protonated primary ethylenimine units of formula (2a):

ii) non-protonated primary ethylenimine units of formula (2b):

iii) protonated secondary ethylenimine units of formula (3a):

wherein the starred bond of the nitrogen is linked to a carbon,

iv) non-protonated secondary ethylenimine units of formula (3b):

wherein the starred bond of the nitrogen is linked to a carbon,

v) protonated tertiary ethylenimine units of formula (4a):

wherein the starred bond of the nitrogen is linked to different carbons,and

vi) non-protonated tertiary ethylenimine units of formula (4b):

wherein the starred bonds of the nitrogen are linked to differentcarbons. More than 0% of the ethylenimine units are present inprotonated form.

In each of the above structures and those that follow, X^(⊖) is anegative-charged counterion bound by non-covalent interactions with thepositive-charged nitrogen labeled 1. Exemplary negative-chargedcounterions include halides (e.g., fluoride, chloride, bromide, iodide),nitrate, hydroxide, methane sulfonate, and carboxylates (e.g., acetate,benzoate). In an embodiment, X^(⊖) is chloride. The cationic polyaminecomprise X^(⊖) groups singularly or in combination.

K′ groups include cyclic and non-cyclic groups, aromatic andnon-aromatic groups, and combinations thereof, comprising one or morealcohol hydroxy groups. In an embodiment, K′ is selected from the groupconsisting of hydroxyalkylene groups, hydroxyalkylenoxy groups, groupscomprising a catechol group, and groups comprising a monosaccharidegroup (sugar moiety). Monosaccharide groups include stereospecific andnon-stereospecific forms of hexose sugars, in particular those ofmannose, glucose, and galactose. These are exemplified in Scheme 2.

The monosaccharide moiety can be linked to the carbonyl group of formula(1) by any suitable linking group including a single bond.

The linking group joining the carbonyl group of formula (1) to the sugarmoiety can be linked to any one of the alcohol hydroxy groups of thesugar moiety.

Non-limiting examples of *—C(═O)K′ groups include those of Scheme 3.

In the above structures the starred bond is linked to the carbonyl groupof formula (1). The backbone nitrogen of formula (1) can complete anamide group, carbamate, or a urea group with the carbonyl group linkedto K′. The cationic polyamine can comprise the K′ groups singularly orin combination.

The cationic polyamine backbone comprises the ethylenimine unitscovalently linked in a head to tail arrangement. Herein, “covalentlylinked” means directly and/or indirectly covalently linked. “Directlycovalently linked” means joined together by a single covalent bond.“Indirectly covalently linked” means covalently linked by way of alinking group. For example, a portion of the chemical structure of thecationic polyamine that contains one or more other ethylenimine units ofthe polymer backbone of the cationic polyamine can be a linking group,which covalently links an N-acylated ethylenimine unit to a protonatedsecondary ethylenimine unit.

The cationic polyamines can further comprise one or more oxidizedethylenimine units of formula (5):

The cationic polyamines can further comprise one or more amideethylenimine units of formula (6):

wherein R′ is methyl, ethyl, propyl, or butyl.

Protonated and non-protonated tertiary ethylenimine units serve asjunction points for intersecting branches. Protonated and non-protonatedprimary ethylenimine units serve as branch terminating units. Herein, ahydrogen linked to a nitrogen of a primary ethylenimine unit can be apolymer chain end group. The cationic polyamines can have other polymerchain end groups.

The cationic polyamines comprise at least one N-acylated ethylenimineunit of formula (1) and at least one cationic ethylenimine unit selectedfrom the group consisting of formula (2a), formula (3a), and formula(4a). More specific cationic polyamines comprise about 100 to about 400ethylenimine units, wherein 1 to about 200 of the ethylenimine units areN-acylated ethylenimine units of formula (1). Still more specificcationic polyamines comprise about 200 to about 300 ethylenimine units,wherein 1 to about 170 of the ethylenimine units are N-acylatedethylenimine units formula (1). Still more specific cationic polyaminescomprise about 200 to about 300 ethylenimine units, wherein 1 to about50 of the ethylenimine units are N-acylated ethylenimine units formula(1).

The end groups of the linear cationic polyamine can be any suitable endgroups such as, for example, hydrogen, alkyl groups, amine groups,hydroxyalkyl groups, and combinations thereof.

A linear cationic polyamine comprises 1 polymer branch comprising apolyethylenimine backbone. More specific linear cationic polyaminescomprise 100 to 400 ethylenimine units, of which 1 to about 200 areN-acylated ethylenimine units of formula (1). The balance of theethylenimine units of the linear cationic polyamine can be secondaryethylenimine units of formula (3a) and (3b). In an embodiment, thelinear cationic polyamine comprises 1 to about 50 oxidized ethylenimineunit of formula (5). In another embodiment, the linear cationicpolyamine comprises 1 to about 30 amide ethylenimine units of formula(6).

A branched cationic polyamine comprises 2 or more intersecting polymerbranches, wherein each of the branches comprises a polyethyleniminebackbone. More specific branched cationic polyamines comprise 100 to 400ethylenimine units, of which 1 to about 170 are N-acylated ethylenimineunits of formula (1). The remaining ethylenimine units includes at least1 tertiary ethylenimine unit and at least 1 secondary ethylenimine unit.At least one of the remaining ethylenimine units is a positive-chargedethylenimine unit of formula (2a), (3a), or (4a). In an embodiment, thebranched cationic polyamine comprises 1 to about 50 oxidizedethylenimine units of formula (5). In another embodiment, the branchedcationic polyamine comprises 1 to about 30 amide ethylenimine units offormula (6).

The cationic polyamines can have a number average molecular weight (Mn)of about 500 to about 100000, more particularly about 1500 to about60000, and most particularly about 5000 to about 60000.

The cationic polyamine can comprise 1 to about 200, more particularly 1to about 150, and most particularly about 4 to about 100 ethylenimineunits of formula (1). In an embodiment, the cationic polyamine has abranched polyethylenimine backbone structure and comprises about 4 toabout 150 ethylenimine units of formula (1). In another embodiment, thecationic polyamine has a branched polyethylenimine backbone structureand comprises about 4 to about 150 ethylenimine units of formula (1),wherein K′ of formula (1) comprises a mannose moiety. In anotherembodiment, the cationic polyamine has a linear polyethyleniminebackbone structure and comprises about 1 to about 70 ethylenimine unitsof formula (1), wherein K′ of formula (1) comprises a mannose moiety.

Preparation of Linear Cationic Polyamines

The cationic polyamines can be prepared from a basic form of apolyethylenimine or a partially N-acylated polyethylenimine. These basepolyamines comprise at least one non-protonated ethylenimine unit offormula (7):

More particularly, linear cationic polyamines can be prepared from basepolyamines that are partially or fully hydrolyzedpoly(2-alkyloxazoline)s. Poly(2-alkyloxazoline)s can be prepared bycationic ring opening polymerization of 2-alkyl oxazolines (Scheme 4).

The ring opening polymerization (ROP) of the 2-alkyl oxazoline can beinitiated by a cationic initiator E′⁺, which becomes a first end groupE′. E″ is a chain terminating second end group. R is typically a C₁-C₁₀alkyl group, more particularly C₁-C₄ alkyl group. Partial hydrolysis ofa poly(2-alkyl oxazoline) using a protic acid followed by neutralizationof the hydrolyzed polymer yields a partially hydrolyzed non-protonatedpoly(2-alkyloxazoline) as shown in Scheme 4, where a+b=n, and a>0 andb>0. A fully hydrolyzed poly(2-alkyloxazoline) is a linearpolyethylenimine (LPEI) homopolymer (a=n and b=0). The ethylenimineunits of the partially or fully hydrolyzed poly(2-alkyloxazoline) arelinked head to tail. In the above bracket notation of Scheme 2, thevertical stacking of the ethylenimine units within the square bracketsindicates a random distribution of the ethylenimine units of the polymerchain. The commercial basic form of a partially hydrolyzedpoly(2-alkyloxazoline) is hemolytic, whereas the protonated partiallyhydrolyzed poly(2-alkyloxazoline) can be less hemolytic.

A method of preparing an antiviral linear cationic polyamine comprisesforming a mixture comprising a base linear polyethylenimine (base LPEI,which can be a partially or fully hydrolyzed poly(2-alkyloxazoline)) andan organic solvent (e.g., chloroform) suitable for conducting anN-acylation. The mixture is optionally heated at an elevated temperaturefor a period of time sufficient to dissolve the base LPEI. The dissolvedbase LPEI is then treated with one or more N-acylating agents, followedby treatment with a protic acid (e.g., methanol/HCl), thereby forming alinear cationic polyamine (modified LPEI) containing ethylenimine unitsof formula (1).

Oxidized ethylenimine units of formula (5) can be introduced into a baseLPEI by treating a mixture comprising the base LPEI and an organicsolvent with air and/or a peroxide. This treatment can be performed atany suitable temperature. Treatment of the oxidized base LPEI with anN-acylating agent followed by acidic workup results in a cationicpolyamine comprising ethylenimine units of formula (1) and oxidizedethylenimine units of formula (5). The backbone amide groups introducedby oxidation can potentially also improve biocompatibility,biodegradability, and/or lower red blood cell toxicity.

Preparation of Branched Cationic Polyamines

The branched cationic polyamines are preferably prepared from a branchedpolyethylenimine (branched PEI or BPEI), which can be formed, forexample, by ring opening polymerization of aziridine. The branched PEIhas 2 or more intersecting polymer chains (branches) comprising backbonenitrogens in the form of primary amine nitrogens, secondary aminenitrogens, and tertiary amine nitrogens, which are alternatingly spacedby backbone ethylene groups (*—CH₂CH₂—*). The branched PEI comprises:

i) 1 or more secondary ethylenimine units of formula (8):

ii) 1 or more tertiary ethylenimine units of formula (9):

which serve as junction points for intersecting branches, andiii) 2 or more primary ethylenimine units of formula (12):

which serve as branch terminating end units.

A branched PEI is also represented herein by formula (13):

wherein j, r, s, and t represent average numbers of the respectiveindependent functional groups of a BPEI macromolecule. Subscript j hasan average value greater than or equal to 4, and r+s+t has an averagevalue greater than or equal to 4. It should be understood by thenotation of formula (13) that each set of parentheses ( ) beginninginside the square brackets [ ] and ending outside the square bracketsencloses an independent functional group of the BPEI, not a polymerchain. Additionally, the atoms having starred bonds represent attachmentpoints to the atoms having starred bonds on the opposite bracket.Additionally, the vertical stacking of the functional groups indicates arandom distribution of the stacked functional groups in the branchedPEI. Each starred bond of a given nitrogen on the right square bracketis linked to a different ethylene group on the left square bracket, andeach starred bond of an ethylene group on the left square bracket islinked to a different nitrogen on the right square bracket, consistentwith the head to tail arrangement of adjacent ethylenimine units.

In an embodiment, j has an average value of about 180 to about 360, rhas an average value of about 90 to about 140, s has an average value ofabout 45 to about 70, t has an average value of about 45 to about 70,and (r+s+t) has an average value of about 180 to about 360. In anotherembodiment, the branched polyethylenimine has a weight average molecularweight (Mw) greater than 1000.

As an example, a commercially available branched polyethylenimine has aweight average molecular weight (Mw) of about 25,000, a number averagemolecular weight (Mn) of about 10,000, and contains an average of 233ethylene groups (j), 116 backbone secondary nitrogens (r), 58 backbonetertiary nitrogens (s), and 58 primary amine nitrogens (t), based on Mnand an average ethylenimine unit molecular weight equal to 43. In thisinstance, j=233, r=116, s=58, and t=58. This material is referred toherein as BPEI25.

As another example, a commercially available branched polyethyleniminehas a weight average molecular weight (Mw) of about 2000, a numberaverage molecular weight (Mn) of about 1800, and contains an average of40 ethylene groups (j), 20 backbone secondary nitrogens (r), 10 backbonetertiary nitrogens (s), and 10 primary amine nitrogens (t), based on Mnand an average ethylenimine unit molecular weight equal to 43. In thisinstance, j=40, r=20, s=10, and t=10. This material is referred toherein as BPEI1.8.

A branched cationic polyamine can be prepared by treating a base form ofa branched PEI with an N-acylating agent capable of introducing one ormore of the above-described N-acyl groups. Treatment of the modifiedbranched PEI with a protic acid provides the branched cationicpolyamine.

If desired, the branched PEI and/or the modified branched PEI can beoxidized as described above to introduce oxidized ethylenimine units offormula (5) for minimizing hemolysis and/or enhancing biodegradability.The oxidation can occur before, during, and/or after formation of themodified branched PEI.

The BPEI used to form the cationic polyamine can have a number averagemolecular weight (Mn) of about 1000 to about 75,000.

Two BPEIs were utilized in the examples further below, designatedBPEI1.8 and BPEI25. BPEI1.8 has Mw of about 2000 and a number averagemolecular weight (Mn) of about 1800. BPEI25 has Mw of about 25,000 andMn of about 10,000.

BPEIs can have a high number of cationic charges and strong capacity toneutralize the endosomal pH. The modified BPEIs can also have abuffering capacity that can be varied by choice of molecular weightand/or degree and type of functionalization of the BPEI. The largenumber of primary amine groups provide sites for subsequenttransformations and installation of a wide variety of functional groups.In this way polymer/cell interactions, polymer/virus interactions, andcytotoxicity can be adjusted.

End Groups

No restriction is placed on the cationic polyamine end groups with theproviso that the end group does not degrade the antiviral properties ofthe polymer.

A linear cationic polyamine comprises a first end group E linked to abackbone nitrogen (labeled 1 above) of an ethylenimine unit. Exemplaryfirst end groups include hydrogen or C₁-C₁₀ alkyl or aryl. A linearcationic polyamine can comprise a second end group E′ linked to aterminal carbon (labeled 3 above) of an ethylenimine unit. Exemplarysecond end groups include primary amine groups (*—NH₂), hydroxy groups(*—OH), and acylated derivatives thereof resulting from reaction withthe N-acylating agents. The end groups of a branched cationic polyaminecan consist essentially of primary ethylenimine units of formula (9) andacylated derivatives thereof. The linear and branched cationicpolyamines can have other end groups.

Alkyl end groups are exemplified by the following chain terminatingunits of the cationic polyamine:

i) secondary ethylenimine units linked to an alkyl substituent R^(e),having formula (14):

wherein R^(e) is a C₁-C₁₀ alkyl or aryl group, andii) acylated ethylenimine units linked to an alkyl substituent R_(e),having formula (15):

wherein R_(e) is a C₁-C₁₀ alkyl or aryl group, and R^(d) is a C₁-C₁₀alkyl group. In an embodiment, R_(e) is methyl or ethyl.

Hydroxy end groups are exemplified by the following chain terminatingunits of linear PEI:

i) protonated secondary ethylenimine units linked to a hydroxy group:

andii) acylated ethylenimine units linked to a hydroxy group:

Amino end groups are exemplified by the following chain terminatingunits of linear PEI:

i) secondary ethylenimine units linked to a protonated primary aminegroup:

andii) acylated ethylenimine units linked to a protonated primary aminegroup:

Other end groups include alkoxy, thiol (*—SH), and substitutedprotonated secondary and tertiary amine groups. Other end groups includederivatives of any of the foregoing groups (e.g., esters and amides ofhydroxy and amino end groups, respectively). The cationic polyamine cancomprise the end groups singularly or in combination.

N-Acylating Agents

The N-acylating agent is a compound capable of reacting with primary orsecondary amine nitrogen of the PEI backbone in one or more processsteps to form an ethylenimine unit of formula (1) comprising a sidechain *—C(═O)K′, where K′ contains at least one alcohol group.

The N-acylating agent comprises an active group for coupling to the PEInitrogen. Non-limiting active groups for N-acylation include carboxylicacid chlorides, carboxylic acid anhydrides, active esters, activecarbonates, cyclic carbonates, lactones, isocyanates, and activecarbamates.

The N-acylating agent can comprise a protected alcohol group, which canbe deprotected after the N-acylation.

The N-acylating agent can comprise a latent form of an alcohol group(e.g., the alcohol group that is formed as a result of the N-acylationas in ring opening of a cyclic carbonate).

Based on these considerations, it will be apparent to skilled artisansthat many compounds are available or can be readily prepared forintroduction of the *—C(═O)K′ side chain.

Preferred N-acylating agents include cyclic carbonates, which canintroduce an alcohol group in one step. Exemplary cyclic carbonatesinclude those of Scheme 5.

Other preferred cyclic carbonates comprise a protected and/orunprotected alcohol groups of a sugar moiety or a catechol group suchas, for example, those of Scheme 6.

Antiviral Properties

For the examples further below, the following definitions areapplicable.

EC50 is defined as the concentration (in mg/L) of cationic polyamine atwhich 50% of the test mammalian cells are not infected by a virus in agiven response time. Small EC50 values are desirable.

CC50 is defined as the concentration (in mg/L) of cationic polyamine atwhich 50% of the test mammalian cells are killed in a given responsetime. High CC50 values are desirable.

Viral selectivity is defined as the CC50/EC50. High viral selectivityvalues are desired.

LD50 is defined as the dose in milligrams of cationic polyamine perkilogram of test animal at which 50% of a test population (e.g., mice)is killed in a given response time. High LD50 values are desirable.

A first method of inhibiting a virus comprises contacting the virus witha cationic polyamine before the virus contacts a mammalian cell, therebyforming a complex comprising the virus and the cationic polyamine boundby non-covalent interactions, thereby inhibiting the virus frominfecting the cell. The buffering capacity of the bound cationicpolyamine can also potentially impede endosomal release of the virusfrom the complex, thereby inhibiting viral replication. Non-limitingexemplary mammalian cell include blood cells, liver cells, nasal cells,lung cells, and cervical cells.

A second method inhibiting a virus comprises contacting a membrane of amammalian cell with a cationic polyamine before the cell contacts avirus, thereby forming a complex comprising the cationic polyamine boundby non-covalent interactions to the cell membrane, wherein the complexinhibits and/or blocks the virus from entering the cell. In anembodiment, the cationic polyamine is bound to a TIM receptor of thecell membrane.

Also disclosed is a method of treating a patient afflicted with adisease caused by a virus, comprising administering a therapeuticallyeffective amount of a disclosed cationic polyamine to the patient,thereby inhibiting and/or curing the disease. In an embodiment, thecationic polyamine is administered by injection. In another embodiment,the cationic polyamine is administered as a solution in the form of anasal spray or inhalation spray. In another embodiment, the cationicpolyamine is administered orally.

Further disclosed is a method of treating and/or preventing a medicalcondition caused by a virus by contacting the virus with a disclosedcationic polyamine, thereby inhibiting the virus from infecting and/orreplicating in a mammalian cell.

Also disclosed is a medical composition for preventing and/or treating aviral infection, comprising one or more of the above-described cationicpolyamines. The medical composition can be a drug. No restriction isplaced on the manner of administration of the drug. The drug can havethe form of a solution, gel, powder, pill, paste, or ointment. The drugcan comprise water. The drug can be administered as an ingestable solid(e.g., pill), an ingestable liquid (e.g., a drink), as a rinse solution(e.g., mouthwash, other hygiene rinse), as intravenous injection, as aspray (e.g., nasal spray), as an inhalant, as a dermal patch, as aliquid drop (e.g., eye drops), and/or as a topically applied ointment(e.g., lotion).

The low average mass, high antiviral activity, and low in vivo toxicity(i.e., high LD50 in mice by intravenous injection) of the cationicpolyamines makes these materials attractive as broad spectrum antiviralagents for a wide range of medical uses, including treating and/orpreventing viral infections.

The following examples demonstrate the preparation and properties of theantiviral cationic polyamines. Non-covalent interactions of virussurface proteins with the mannose functionalized branchedpolyethylenimine were found. Interactions with respect to binding andprevention of virus uptake appear to be generally applicable to a widevariety of viruses. Other interactions such as the number ofhydrogen-bonds required to form a viral/polymer complex can be virusspecific. The supramolecular polymer-virus interactions provide broadspectrum activity with high selectivity. The generality of thishydrogen-bonded virus/polymer complex appears to be unaffected bysubsequent viral mutation, which aids in preventing the onset of viralresistance. Thus, the polymer/virus complex can be exploited to preventviral infection.

EXAMPLES

Materials used in the following examples are listed in Table 1.

TABLE 1 ABBREVIATION DESCRIPTION SUPPLIER BPEI1.8 BranchedPolyethylenimine, Mw = 2000, Mn = Sigma-Aldrich 1800, 10 primary aminegroups, 20 secondary amine groups and 10 tertiary amine groups BPEI25Branched Polyethylenimine, Mw = 25000, Mn = Sigma-Aldrich 10000, PDI2.5, 58 primary amine groups, 116 secondary amine groups and 58 tertiaryamine groups LPEI25 Linear Polyethylenimine Mw = 25000, Mn =Polysciences 10950, PDI 1.16; 2 primary amine end groups, 246 secondaryamine groups, 8 acylated amine groups. MTT(3-(4,5-Dimethylthiazol-2-yl)-2,5- Sigma-Aldrich diphenyltetrazoliumbromide IPMAN 2,3;5,6-Di-O-Isopropylidene-D-Mannofuranose Sigma-AldrichHEPES 4-(2-Hydroxyethyl)-1-Piperazineethanesulfonic Invitrogen Acid EMEMEagle's Minimum Essential Medium Sigma-Aldrich DMEM Dulbecco's ModifiedEagle's Medium Biowest FBS Fetal Bovine Serum Invitrogen PBS PhosphateBuffered Saline Sigma-Aldrich PBMC Peripheral Blood Mononuclear CellNITD008 (2R,3R,4R,5R)-2-(4-aminopyrrolo[2,3- Novartisd]pyrimidin-7-yl)-3-ethynyl-5- (hydroxymethyl)oxolane-3,4-diol DBU1,8-Diazabicyclo[5,4,0]undec-7-ene Sigma-Aldrich TMC TrimethyleneCarbonate Sigma-Aldrich Bis-MPA 2,2-Dimethylol-Propionic AcidSigma-Aldrich PFC Bis-pentafluorophenyl carbonate Iris Biotech GmbH

Herein, Mn is the number average molecular weight, Mw is the weightaverage molecular weight, and MW is the molecular weight of onemolecule.

Solid branched polyethylenimine (BPEI25, Mn 10,000, PDI 2.5) wasfreeze-dried prior to use.

Peripheral blood mononuclear cells (PBMC) and macrophages were derivedfrom human blood from healthy adult individuals after informed consent.

Anhydrous solvents were dried using activated alumina columns and storedover molecular sieves (3 Å).

¹H NMR spectra were acquired on a Bruker Avance 400 instrument at 400MHz. Gel permeation chromatography (GPC) was performed intetrahydrofuran (THF) using a Waters system equipped with four5-micrometer Waters columns (300 mm×7.7 mm) connected in series withincreasing pore size (100, 1000, 105, and 106 angstroms), a Waters 410differential refractometer, and a 996 photodiode array detector. Thesystem was calibrated using polystyrene standards. GPC analysis was alsoperformed in N,N-dimethylformamide (DMF) spiked with 0.01 M LiBr using aWaters system equipped with two Agilent PolyPore columns (300 mm×7.5 mm)connected in series, a Waters 410 differential refractometer. The systemwas calibrated with poly(methyl methacrylate) standards.

Preparations of Cyclic Carbonates

Preparation of MTC-OH (MW 160.1).

MTC-OH can be prepared by the method of R. C. Pratt, et al., ChemicalCommunications, 2008, 114-116.

Preparation of MTC-C6F5 (MW 326.2).

A 100 mL round bottom flask was charged with bis-MPA, (7), (5.00 g, 37mmol, MW 134.1), bis-(pentafluorophenyl) carbonate (PFC, 31.00 g, 78mmol, MW 394.1), and CsF (2.5 g, 16.4 mmol) rinsed with 70 mls oftetrahydrofuran (THF). Initially the reaction was heterogeneous, butafter one hour a clear homogeneous solution was formed that was allowedto stir for 20 hours. The solvent was removed in vacuo and the residuewas re-dissolved in methylene chloride. The solution was allowed tostand for approximately 10 minutes, at which time the pentafluorophenolbyproduct precipitated and could be quantitatively recovered. Thispentafluorophenol byproduct showed the characteristic 3 peaks in the ¹⁹FNMR of pentafluorophenol and a single peak in the GCMS with a mass of184. The filtrate was extracted with aqueous sodium bicarbonate anddried with MgSO₄. The solvent was evaporated in vacuo and the productwas recrystallized (ethyl acetate/hexane mixture) to give MTC-C6F5 as awhite crystalline powder. The GCMS had a single peak with mass of 326g/mol. The calculated molecular weight for C₁₂H₇F₅O₅ was consistent withthe assigned structure. ¹H-NMR (400 MHz in CDCl₃): delta 4.85 (d, J=10.8Hz, 2H, CH_(a)H_(b)), 4.85 (d, J=10.8 Hz, 2H, CH_(a)H_(b)), 1.55 (s, 3H,CCH₃).

Example 1. Synthesis of Protected Mannose-Functionalized CyclicCarbonate (MTC-IPMAN)

5-Methyl-5-carboxyl-1,3-dioxan-2-one (MTC-OH) and the monomer MTC-ipmanwere prepared as follows. A dry tetrahydrofuran (THF) solution of oxalylchloride (2.48 mL, 19.0 mmol, 50 mL) was added dropwise into a dry THFsolution of 5-methyl-5-carboxyl-1,3-dioxan-2-one (MTC-OH) (2.75 g, 17.2mmol, 50 mL). A catalytic amount (3 drops) of anhydrousdimethylformamide (DMF) was then added over 30 min under nitrogenatmosphere, and the reaction mixture was stirred for 1 hour withnitrogen bubbled through to remove volatiles. After the solvent wasevaporated under vacuum, the solid residue (intermediate product MTC-Cl)was dissolved in 50 mL of dry chloroform, and a mixture of2,3;5,6-di-O-isopropylidene-D-mannofuranose (IPMAN, 4.13 g, 15.8 mmol)and triethylamine (2.8 mL, 20.6 mmol) in 50 mL of dry chloroform wasstepwise dropped into the solution over 30 minutes at room temperature.The reaction mixture was heated to 40° C. and stirred for 48 hours. Theresulting solution was cooled to room temperature, concentrated, treatedwith THF (100 mL) to precipitate triethylamine salt, and filtered. Afterevaporating the filtrate, the crude product was passed through a silicagel column by gradient eluting of ethyl acetate and hexane (20/80 to50/50) to provide the product as sticky colorless oil that slowlysolidified to a white solid (5.85 g, 85%). ¹H-NMR (400 MHz, CDCl₃, 22°C.): δ 6.22 (s, 1H, H-a), 4.89 (dd, 1H, H-b), 4.72 (d, 2H, H-c), 4.66(m, 2H, H-c), 4.41 (m, 1H, H-d), 4.22 (m, 2H, H-e), 4.11 (dd, 2H, H-e),4.03 (m, 2H, Hf+H-g), 1.50-1.33 (5 s, 15H, H-h+H-i).

Preparation of MTC-Catechol.

2-Hydroxyethyl-3,4-bis(benzyloxy)benzoate (HEBB, 2.81 g, 7.42 mmol),MTC-C6F5 (2.54 g, 7.79 mmol) and PROTON SPONGE (1.59 g, 7.42 mmol) weredissolved in THF (10 mL) and stirred overnight at room temperature. Oncethe reaction was completed, a mixture of diethyl ether and hexanes wasadded, and the solution was left for several hours at −40° C. Whitecrystals were obtained and washed with diethyl ether and hexanes. Yield:2.0 g (71%). ¹H NMR (400 MHz, CDCl₃, 22° C.): delta 7.64 (d, 2H, H ofbenzoate), 7.43 (m, 10H, —OCH₂PhH), 6.97 (d, 1H, H of benzoate), 5.24(d, 4H, —OCH₂PhH), 4.68 (d, 2H, —CH2OCOO—), 4.54 (s, 4H, —COOCH₂CH₂O—),4.19 (d, 2H, —CH2OCOO—), 1.32 (s, 3H, —CH₃).

Preparation of BPEI25 and BPEI1.8 Conjugates

In the following examples, the structures of BPEI25 and BPEI1.8 arerepresented by following notation:

BPEI25 BPEI1.8 Mw = 25 kDa Mw = 2 kDa Mn = 10 kDa Mn = 1.8 kDa q = 116 q= 20 s = 58 s = 10 t = 58 t = 10 j = 233 j = 40

The subscript q represents the number of secondary amine groups (pKa8.6). For BPEI25, q=116. The subscript s represents the number oftertiary amine groups (pKa 7.5). For BPEI25, s=58. The subscript trepresents the number of primary amine groups (pKa 9.6). For BPEI25,t=58. The subscript j represents the number of ethylene groups. ForBPEI25, j=233. Thus, BPEI25 is a hyperbranched polymer having an averageof 233 ethylene groups, 58 primary amine groups, 116 secondary aminegroups, 58 tertiary amine groups per mole. For the reactions below, 1mole=10000 g=Mn.

BPEI1.8 has an average of 40 ethylene groups, 10 primary amine groups,20 secondary amine groups, and 10 tertiary amine groups per mole. Forthe reactions below, 1 mole=1800 g=Mn.

It should be understood that each starred bond of a given nitrogen ofthe right bracket is linked to a different ethylene group of the leftbracket, and each starred bond of a given ethylene group on the leftbracket is linked to a different nitrogen on the right bracket. Thus,the BPEI backbone comprises alternating amine nitrogens and ethylenegroups (i.e., adjacent ethylenimine units are linked in head-to-tailarrangement). The tertiary, secondary and primary amine groups arerandomly distributed in BPEI, indicated by the vertical stacking of theamine groups on the right square bracket. BPEI can contain numerousbranches that intersect at the tertiary amine sites. Depending on themethod of formation of the BPEI, peripheral end groups (dangling endgroups) can be a primary amine group, alkyl group, or another C₁-C₁₀moiety. In the examples below, branches terminate at a peripheral endwith a primary amine group. In the above notation, all peripheral endgroups (dangling end groups) are primary amine groups.

A selected number of the primary and/or secondary amine groups on BPEI25were modified with a mannose-substituted cyclic carbonate MTC-IPMAN. Thering-opening reaction generates a side chain containing a carbamate sidechain containing a protected mannose functionality. Deprotection of theprotected mannose groups yields a side chain bearing a mannose group. Anadditional benefit of this modification is a significant reduction intoxicity of the modified BPEI25 compared to the non-modified BPEI25.

Examples 2 to 7

Preparation of B1-B6 by modifying BPEI25 (Mn 10,000=1 mole) withMTC-IPMAN. The modification of BPEI25 is illustrated below for thepreparation of B3 (Example 4). For B3, MTC-IPMAN was used in excess ofthe primary amine groups of BPEI25. Under these conditions, MTC-IPMANdoes not undergo ring opening polymerization. About 100% of the BPEI25primary amine groups and about 6% of the BPEI25 secondary amine sitesare modified with one ring opened molecule of MTC-IPMAN. Subsequent acidcatalyzed hydrolysis of the isopropylidene ketal protecting groupsresults in a modified BPEI25 containing 65 mannose units linked to thePEI backbone by respective carbamate linking groups.

In a glove box, MTC-IPMAN (0.302 g, 0.75 mmol, MW=402.15 g) was added tothe solution of BPEI25 (0.1 g, 0.01 mmol based on 1 mole=10,000 g=Mn) in2 mL of dichloromethane (DCM). The BPEI25:MTC-IPMAN feed mass ratio was1:3, the molar ratio was 1:75. The reaction solution was stirred for 1hour. 10 mL of methanol and 10 mL of 1 M HCl (aq.) were added. Theresulting reaction mixture was heated at reflux for 2 hours beforecooling to room temperature. Finally, the above mixture was purified byultrafiltration in a Vivaspin 20 concentrator (MWCO=5000, Sartorius AG,Goettingen, Germany), washed 3 times with de-ionized (DI) water, andfreeze-dried (0.19 g, 48%). ¹H-NMR (400 MHz, D₂O, 22° C.): delta 4.11(s, 130H, H-d and H-e), 2.56-3.70 (br, m, 1190H, H-e, H-f, H-g and H ofBPEI), 1.10 (s, 195H, H-i).

In the above structure of B3, s′ represents the number of protonatedtertiary amine groups, q′ represents the number of remaining secondaryamine groups in the form of a protonated salt, t′ represents the numberof remaining primary amine end groups in the form of a protonated salt,u represents the number of modified secondary amine groups bearing themoiety M′, and v represents the number of modified primary amine groupsbearing the moiety M′. For B3, q′=109, s′=58, t′=0, u=7, v=58, andu+v=65.

The amine modification level of B3 was monitored and quantified using¹H-NMR (FIG. 1). For example, relative integral intensities of a broadpeak (2.56-3.70 ppm), which are attributed to the protons of BPEI25methylene and H-e, H-f and H-g of mannose moieties, and MTC methylsignals (1.10 ppm) in the ¹H-NMR spectrum were compared in order todetermine the number of mannose groups. More of the secondary aminesites were modified in B4-B6, where the number of mannose groupsintroduced was 86, 104 and 143, respectively.

B1 (Example 2) was prepared by reaction of BPEI25 (0.2 g, 0.02 mmol)with MTC-IPMAN (201 mg, 0.5 mmol) in dichloromethane following the abovegeneral procedure for B3 (Example 4). A total of 28 mannose groups wereintroduced (BPEI25:MTC-IPMAN molar ratio: 1:28). For B1, q′=116, s′=58,t′=30, u=0, v=28, and u+v=28.

B2 (Example 3) was prepared by reaction of BPEI25 (0.12 g, 0.012 mmol)with MTC-IPMAN (280 mg, 0.7 mmol) in dichloromethane following the abovegeneral procedure for B3 (Example 4). A total of 51 mannose groups wereintroduced (BPEI25:MTC-IPMAN molar ratio: 1:51). For B2, q′=116, s′=58,t′=7, u=0, v=51, and u+v=51.

The ring opening reaction is increasingly affected by steric hindrancewith an increased degree of modification, requiring more forcingconditions to obtain the desired level of modified amine groups at thehigher modification levels.

B4 (Example 5) was prepared by reaction of BPEI25 (58 mg, 0.0058 mmol)with MTC-IPMAN (280 mg, 0.7 mmol) in dichloromethane following the abovegeneral procedure for B3 (Example 4) except the reaction was stirred 2.5hours at ambient temperature. A total of 86 mannose groups wereintroduced (BPEI25:MTC-IPMAN molar ratio: 1:86). For B4, q′=88, s′=58,t′=0, u=28, v=58, and u+v=86.

B5 (Example 6) was prepared by reaction of BPEI25 (70 mg, 0.007 mmol)with MTC-IPMAN (338 mg, 0.84 mmol) in dichloromethane following theabove general procedure for B3 (Example 4), except the reaction wasstirred 3 hours at 40° C. A total of 104 mannose groups were introduced(BPEI25:MTC-IPMAN molar ratio: 1:104). For B5, q′=70, s′=58, t′=0, u=46,v=58, and u+v=104.

B6 (Example 7) was prepared by reaction of BPEI25 BPEI25 (50 mg, 0.005mmol) with MTC-IPMAN (362 mg, 0.9 mmol) in dichloromethane following theabove general procedure for B3 (Example 4), except the reaction wasstirred 3 hours at 40° C. A total of 143 mannose groups were introduced(BPEI25:MTC-IPMAN molar ratio: 1:143). For B6, q′=31, s′=58, t′=0, u=85,v=58, and u+v=143.

Examples 8 and 9

Preparation of B7 and B8 by modifying BPEI25 with trimethylene carbonate(TMC). The preparation of B7, in which 25 TMC units were introduced, isshown in the following reaction diagram.

B7 (Example 8) was prepared by reaction of BPEI25 (0.25 g, 0.025 mmol)with TMC (64 mg, 0.63 mmol) in dichloromethane following the abovegeneral procedure for B3 (Example 4). A total of 25 TMC groups wereintroduced. For B7, q′=116, s′=58, t′=33, u=0, v=25, and u+v=25.

B8 (Example 9) was prepared by reaction of BPEI25 (0.25 g, 0.025 mmol)with TMC (191 mg, 1.87 mmol) in dichloromethane following the generalprocedure for B3 (Example 4). A total of 75 TMC groups were introduced.For B8, q′=99, s′=58, t′=33, u=17, v=58, and u+v=75.

Examples 10 to 12

Preparation of B9 to B11 by modifying of BPEI25 with MTC-catechol. Thepreparation of B9 (Example 10) is representative, wherein 5 MTC-catecholgroups are introduced. The hydrogen reduction of the protected catecholgroups can leave 0 or more protected catechol groups in the finalproduct.

BPEI25 (0.3 g, 0.03 mmol) was treated with MTC-catechol (62.4 mg, 0.12mmol) in dichloromethane according to Example 2. A total of 5 protectedcatechol groups were introduced. The resulting product was dried invacuum. A mixture of the protected conjugate (362 mg), MeOH (7.5 mL),THF (7.5 mL), and Pd—C (10% w/w, 0.2 g) was swirled under H₂ (7 atm)overnight. After evacuation of the hydrogen atmosphere, the mixture wasfiltered by syringe and the filtrate was concentrated to dryness. Then,MeOH (10 mL) and 1 M HCl (10 mL) were added sequentially and thereaction solution was stirred for 2 to 3 hours. After acidification, thesolution was purified by centrifugal filtration (MWCO=3,000) and washedtwice with deionized (DI) water for three times. Finally, theconcentrated solution in the centrifuge tube was freeze-dried, yieldingthe deprotected and acidified BPEI-Catechol conjugate B9 (0.43 g, 53%).¹H-NMR (400 MHz, D₂O, 22° C.): ¹H-NMR (400 MHz, D₂O, 22° C.): delta6.70-7.60 (br, m, 15H, PhH), 3.90-4.40 (br, m, 10H, —CH₂OCOO), 2.50-3.70(br, m, 950H, H of —CH₂CH₂OC(O)Ph and BPEI25), 1.03 (m, 15H, —CH₃).

For B9, q′=116, s′=58, t′=53, u=0, u′=0, v 0, v′>=0, and u+u′+v+v′=5.

B10 (Example 11) was prepared by reaction of BPEI25 (0.3 g, 0.03 mmol)with MTC-catechol (124.8 mg, 0.24 mmol) in dichloromethane following thegeneral procedure of Example 10. A total of 12 catechol groups wereintroduced. For B10, q′=116, s′=58, t′=46, u=0, u′=0, v>0, v′≧=0, andu+u′+v+v′=12.

B11 (Example 12) was prepared by reaction of BPEI25 (0.2 g, 0.02 mmol)with MTC-catechol (167 mg, 0.32 mmol) in dichloromethane following thegeneral procedure of Example 10. A total of 20 catechol groups wereintroduced. FIG. 2A is a ‘E1 NMR spectrum taken in MeOD beforehydrogenolysis. FIG. 2B is a ¹H NMR spectrum taken in D₂O of B11 afterhydrogenolysis and acidification. For B11, q’=116, s′=58, t′=38, u=0,u′=0, v>0, v′≧=0, and u+u′+v+v′=20.

Preparation of BPEI1.8 Conjugates

BPE1.8 has Mw 2000 and Mn 1800. BPEI1.8 has q=20 secondary amine groups,s=10 tertiary amine groups, t=10 primary amine groups, and j=40 ethylenegroups. For the calculations below, 1 mole BPEI1.8=1800 g.

Examples 13 to 15

Preparation of B12 to B14, respectively, by modifying BPEI1.8 (Mn 1800=1mole) with MTC-IPMAN. The preparation of B12 (Example 13) is shown inthe reaction diagram below, for which 4 mannose groups were introduced.

B12 (Example 13) was prepared by reaction of BPEI1.8 (0.198 g, 0.11mmol) with MTC-IPMAN (199 mg, 0.495 mmol) in dichloromethane followingthe general procedure used for B3 (Example 4). A total of 4 mannosegroups were introduced.

In the above structure for B12, s′ represents the number of protonatedtertiary amine groups, q′ represents the number of remaining secondaryamine groups in the form of a protonated salt, t′ represents the numberof remaining primary amine end groups in the form of a protonated salt,u represents the number of modified secondary amine groups bearing themoiety M′, and v represents the number of modified primary amine groupsbearing the moiety M′. For B12, q′=20, s′=10, t′=6, u=0, and v=4, andu+v=4.

B13 (Example 14) was prepared by reaction of BPEI1.8 (0.108 g, 0.06mmol) with MTC-IPMAN (326 mg, 0.81 mmol) in dichloromethane followingthe general procedure used for B3 (Example 4). A total of 9 mannosegroups were introduced. For B13, q′=20, s′=10, t′=1, u=0, and v=9, andu+v=9.

B14 (Example 15) was prepared by reaction of BPEI1.8 (0.072 g, 0.04mmol) with MTC-IPMAN (348 mg, 0.864 mmol) in dichloromethane followingthe general procedure used for B3 (Example 4). A total of 17 mannosegroups were introduced. For B13, q′=13, s′=10, t′=0, u=7, and v=10, andu+v=17.

Preparation of LPEI25 Conjugates

LPEI25 is a linear polyethyleneimine having Mw=25000, Mn=10950, PDI1.16; 0 primary amine end groups, 247 secondary amine groups (x), and 8acylated secondary amine groups (y), represented by the notation below.

Vertical stacking of the repeat units within the square bracketsrepresents a random distribution of the repeat units. End group E ismethyl and end group E′ is OH. E′ and E″ are not limited to these endgroups. For the following examples, 1 mole LPEI25=10950 grams.

Examples 16 to 18

Preparation of mannose modified LPEI25 polymers L1 to L3 (polymers t tov), respectively. The preparation of L1 is representative, where 8mannose groups were introduced.

LPEI25 (0.35 g, 0.032 mmol) was heated for 3 hours in a flask at 65° C.in vacuum. When the flask cooled to room temperature, dioxane (30 mL)was added to the flask. Then, the flask was charged with condenser andheated to 85° C. After all the LPEI25 was dissolved in dioxane and ahomogeneous solution was obtained, a solution of MTC-IPMAN (50 mg, 0.12mmol) in 10 mL of dioxane was added. The reaction mixture was stirredovernight at 85° C. in contact with air. The flask cooled to roomtemperature, and the solvent was removed by rotary evaporation. Theresulting product was dried in vacuum. For L1, x′=239, y=8, and z=8.

The above conjugate was dissolved in MeOH (10 mL) and 1 M HCl (10 mL).The solution was heated at reflux for 2 hours and cooled to roomtemperature. The resulting solution was purified by centrifugalfiltration (MWCO=2,000) and washed three times with deionized (DI)water. Finally, the concentrated solution in the centrifuge tube wasfreeze-dried, yielding the acidified LPEI-Man conjugate L1 (0.47 g,80%). ¹H-NMR (400 MHz, D₂O, 22° C.): delta 3.00-4.00 (m, 1059H, H ofLPEI and mannose), 2.37 (m, 16H, CH₃CH₂CONH—), 1.06 (m, 24H,CH₃CH₂CONH—), 0.96 (m, 24H, —CH₃).

L2 was prepared by reaction of LPEI25 (0.3 g, 0.027 mmol) with MTC-IPMAN(100 mg, 0.25 mmol) following the general procedure of Example 16. Atotal of 15 mannose groups were introduced. For L2, x′=232, y=8, andz=15.

L3 was prepared by reaction of LPEI25 (0.2 g, 0.018 mmol) with MTC-IPMAN(200 mg, 0.5 mmol) following the general procedure of Example 16. Atotal of 26 mannose groups were introduced. For L3, x′=221, y=8, andz=26.

Table 2 summarizes the preparations of the modified BPEI25 and LPEI25polymers of Examples 2-18.

TABLE 2 # % of Amine Amine Cyclic Groups Groups Example Name PEICarbonate Modified Modified Mn^(a) 2 B1  BPEI25 MTC-IPMAN 28 12.0 19,0163 B2  BPEI25 MTC-IPMAN 51 21.9 26,422 4 B3  BPEI25 MTC-IPMAN 65 27.930,930 5 B4  BPEI25 MTC-IPMAN 86 36.9 37,692 6 B5  BPEI25 MTC-IPMAN 10444.6 43,488 7 B6  BPEI25 MTC-IPMAN 143 61.4 56,046 8 B7  BPEI25 TMC 2510.7 12,550 9 B8  BPEI25 TMC 75 32.2 17,650 10 B9  BPEI25 MTC-Catechol 52.1 11,700 11 B10 BPEI25 MTC-Catechol 12 5.2 14,080 12 B11 BPEI25MTC-Catechol 20 8.6 20,880 13 B12 BPEI25 MTC-IPMAN 4 1.7 3,088 14 B13BPEI25 MTC-IPMAN 9 3.9 4,698 15 B14 BPEI25 MTC-IPMAN 17 7.3 7,274 16 L1 LPEI25 MTC-IPMAN 8 20.0 13,526 17 L2  LPEI25 MTC-IPMAN 15 37.5 15,780 18L3  LPEI25 MTC-IPMAN 26 65.0 19,322 ^(a)Obtained from ¹H NMR.

Titration Experiments

The number of mannose modified amine groups of B1 to B6 was 28, 51, 65,86, 104, and 143, respectively. Acid-base titration experiments wereperformed with polymers B1 to B6 to evaluate their relative pHneutralization capacity (buffering capacity).

A given polymer (0.1 mmol of all amines excluding those reacted withmannose-functionalized cyclic carbonate) was first dissolved in NaClsolution (7.5 mL, 150 mM). HCl solution (22.5 mL, 0.01 N) was added tobring the pH down to 2 and the solution was then titrated against 0.01 NNaOH to pH 10 using an auto titrator (Spectralab Instruments).Unmodified BPEI25 (Mn 10 kDa) was used as a control. The bufferingcapacity is defined as the percentage of amine groups of the polymerthat are protonated over the pH of 5.0 to 7.4, and is calculated by thefollowing equation: buffering capacity (%)=100×V_(NaOH)×0.01×40)/W,where V_(NaOH) is the volume of NaOH (0.01 N, MW 40), which is requiredto increase the pH from 5.0 to 7.4, and W is the weight (in milligrams)of the polymers.

Table 3 lists the buffering capacities of BPEI25 and B1 to B6.

TABLE 3 # Modified Buffering Starting Amine capacity Example Name PEICyclic Carbonate Groups (%) Control BPEI25 0 24.2 2 B1 BPEI25 MTC-IPMAN28 16.3 3 B2 BPEI25 MTC-IPMAN 51 10.9 4 B3 BPEI25 MTC-IPMAN 65 8.8 5 B4BPEI25 MTC-IPMAN 86 7.5 6 B5 BPEI25 MTC-IPMAN 104 7.2 7 B6 BPEI25MTC-IPMAN 143 5.7

As indicated above, the neutralization capacity of the endosomal pH from5.0 to 7.4 decreased with increasing mannose content at the same weightconcentration of polymers due to a reduced number of secondary aminesand/or increased molecular weight, which lowers the tertiary aminecontent per unit mass of the polymer.

Anti-Viral Activity Cells

LLC-MK2 cells (monkey kidney cell) were cultured in Eagle's minimumessential medium (EMEM, Sigma-Aldrich, St. Louis, Mo.) supplemented with10% fetal bovine serum (FBS, Invitrogen, Carlsbad, Calif.), 100 units/mLpenicillin and 100 micrograms/mL streptomycin at 37° C. in 5% CO₂.

Aedes albopictus C6/36 cells were maintained in Roswell Park MemorialInstitute (RPMI) medium RPMI-1640 (Invitrogen, Carlsbad, Calif.) withHEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, 25 mM)supplemented with 10% FBS (fetal bovine serum), 100 U/mL penicillin and100 micrograms/mL streptomycin, and incubated at 28° C. in 5% CO₂.

A549 replicon cells (containing DENV-2 NS genes), Vero cell line (monkeykidney epithelial), MDCK cell line (dog kidney epithelial), and RD cellline (human muscle spindle cell, rhabdomyosarcoma) were grown inDulbecco's modified Eagle's medium (DMEM) supplemented with 10% FBS, 100U/mL penicillin and 100 micrograms/mL streptomycin at 37° C. in 5% CO₂.

Viruses

Clinical samples of DENV-1 and DENV-4 and laboratory-adapted New GuineaC (NGC) strain of DENV-2 were kindly provided by Dr. Justin JH Chu(National University of Singapore, Singapore). DENV-3 strain EDEN8630K1was isolated by the method of Low, et al., “Early Dengue Infection andOutcome Study (EDEN)—Study Design and Preliminary Findings”, AnnalsAcademy of Medicine Singapore 2006, 35, pages 783-789. The viruses werepropagated in various cell lines as described in further below (Table5). The supernatant from infected cells was centrifuged to remove celldebris, then aliquoted and stored at −80° C.

Anti-Viral Activity Based on Cytotoxicity Assay

Anti-dengue virus activity and cytotoxicity of polymers in LLC-MK2 cellswere monitored by infecting the cells with DENV (i.e., DENV-1, DENV-2,DENV-3, or DENV-4). Infected (multiplicity of infection (MOI): 0.5) andnon-infected cells were exposed to a range of concentrations of polymers(cell seeding density in 96-well plate: 2000 per well), and allowed toproliferate for 5 days. The number of viable cells was quantified by the3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT)(Sigma-Aldrich, St. Louis, Mo.) assay to obtain EC50 (from infectedcells) and CC50 (from non-infected cells).

Plaque Forming Assay

For EC50 determination of polymers, virus was added to LLC-MK2 cells in6-well plates (cell seeding density: 3×10⁵) with polymers at variousconcentrations at MOI of 100 pfu per well, and incubated at 4° C. for 90min. The medium was then removed, and the cells washed with cold PBS (pH7.4) before the cells were incubated with medium containing polymers atthe corresponding concentrations at 37° C. At 5 days post-inoculation,the cells were fixed with 4% paraformaldehyde in PBS (pH 7.4) at roomtemperature for 20 minutes. Next, they were washed with water before theaddition of 1 mL of 1% crystal violet at room temperature for 20minutes. The plates were washed and dried, and the plaque forming unitsper milliliter (pfu/mL) were counted and calculated to obtain EC50.

Time of Addition Experiment

LLC-MK2 cells were seeded at 30×10⁴ cells/well in 6-well plates. Thecells were incubated with DENV-2 (100 pfu per well) at 4° C. for 90 minon a rocking platform. The cells were then washed 3 times with cold PBSand the plates were shifted to a 37° C. incubator and cultured. Culturemedium containing 50 mg/L of B3 or 100 mg/L of heparin (MP Biomedicals,Solon, Ohio) was added to the cells at pre-determined time points (−1.5,0, 1, 2, 3, 4 and 5 hours). After 5 days of incubation at 37° C., viralinhibition activity was studied by the plaque assay. Experiments wereconducted in triplicates and mean percentage inhibition was calculatedrelative to the control, which was performed under the same conditionsbut without polymers.

Virus Binding Assay

DENV-2 was incubated with PBS (pH 7.4) or PBS containing B3 (50 mg/L) at4° C. for one hour to allow the polymer to bind onto the virus. Unboundpolymer molecules were then removed by filtration through a Vivaspin500, 100 kDa molecular weight cut off (GE Healthcare, Buckinghamshire,UK) at 6000 grams for 15 minutes. The virus was subjected to the plaqueassay as described above to determine titers.

Cell Binding Assay

LLC-MK2 cells were treated with B3 (50 mg/L) at 37° C. for 2 hours, 1hour, 30 minutes, and 15 minutes, and washed with PBS. The cells werethen infected with DENV-2 for 90 minutes, and inoculated at 37° C. for 5days prior to plaque reduction assay. Control infection without thepolymer was set to 100%. The data were expressed as the mean of threeindividual experiments±SD (standard deviation).

Cell Fusion Inhibition Assay

This assay was used to detect the inhibition of cell fusion by polymersat low pH. C6/36 cells were seeded with a cell density of 1.0×10⁶cells/well in 6-well plates one day prior to the assay. DENV-2 wasinoculated at multiplicity of infection (MOI) 0.03 onto seeded C6/36cells along with either 50 mg/L of B3, 100 mg/L of heparin, or medium,for 90 minutes at 4° C. The plates were then washed 3 times with PBS.Fresh medium containing the polymer/heparin was added to the plates, andthe cells were incubated at 28° C. for 2 days. Thereafter, the mediumwas acidified to induce fusion by addition of 50 microliters of 0.5 M2-(N-morpholin) ethanesulfonic acid (MES) (pH 5.0) (Sigma-Aldrich, St.Louis, Mo.), followed by incubation at 28° C. for 2 days. Fusion cellswere then stained with Giemsa stain, modified solution (Sigma-Aldrich,St. Louis, Mo.) according to manufacturer's protocol. The stained plateswere analyzed under a light microscope (CKX 31 microscope, Olympus,Tokyo, Japan). In another set of experiments, virus and cells wereincubated for 90 minutes at 4° C. before the polymer or heparin wasadded.

Evaluation of Drug Resistance

Drug resistance was studied by passaging DENV-2 on LLC-MK2 cells in thepresence of B3 at EC50. Cells (3×10⁵ per well) in 6-well plates wereinfected by DENV-2 (obtained from the previous passaging) at MOI of 0.1in the presence of B3 at EC50. EC50 was determined for each passaging bythe plague forming assay as described above.

In Vivo Toxicity Studies by Injection

Animal studies were performed according to protocols approved by theSingapore Biological Research Center (BRC)'s Institutional Animal Careand Use Committee and IBM's Animal Care and Use Committee. Female Balb/cmice (6-7 weeks, 18-22 g) were used in all experiments for studies ofLD50 and toxicity to the major organs liver and kidney, and electrolytebalance in the blood.

LD50 (dose required to kill half the mouse population for a given testduration) was determined according to the Up-and-Down-Proceduredescribed in OECD Guidelines for the Testing of Chemicals (OECD 425).Twenty mice were observed for 7 days and randomly marked to permitindividual identification. B2 or B3 was dissolved in PBS (pH 7.4), andgiven to mice via tail vein injection at designed doses (i.e., 56.0,175, 560 and 1750 mg/kg, 0.1 mL). Mortality was monitored for 14 dayspost-treatment, and LD50 was determined using the maximum likelihoodmethod.

For the evaluation of the acute toxicity, two groups of 10 mice eachreceived intravenous injection of B3 at 60 mg/kg in 100 microliters ofsterilized saline. Ten mice were sacrificed at 48 hours and theremaining mice at 14 days to collect blood samples for analysis of ALT,AST, total bilirubin (TBIL), creatinine, urea nitrogen, sodium ion andpotassium ion levels.

Results Anti-Viral Activity and Selectivity of Modified PEI Polymers

Anti-viral activity of unmodified and modified PEI polymers (branchedand linear) was investigated by a conventional MTT assay using LLC-MK2cells infected with DENV-2 (dengue virus-2). Table 4 lists the EC50,CC50, and selectivity (CC50/EC50) obtained for BPEI25, BPEI1.8, B1-B14,and L1-L3 when the virus, cells and polymer were incubated at the sametime.

TABLE 4 # Modified Selectivity^(c) Amine EC50^(a) CC50^(b) (CC50/Example Name PEI Cyclic Carbonate Groups (mg/L) (mg/L) EC50) Mn^(d)Control BPEI25 0 0.01 5.44 544 10,000 2 B1  BPEI25 MTC-IPMAN 28 0.1226.7 223 19,016 3 B2  BPEI25 MTC-IPMAN 51 0.4 697 1743 26,422 4 B3 BPEI25 MTC-IPMAN 65 0.3 >1000 >3333 30,930 5 B4  BPEI25 MTC-IPMAN 860.99 >1000 >1010 37,692 6 B5  BPEI25 MTC-IPMAN 104 3.33 >1000 >30043,488 7 B6  BPEI25 MTC-IPMAN 143 50.5 >1000 >19.8 56,046 8 B7  BPEI25TMC 25 0.035 23.7 672 12,550 9 B8  BPEI25 TMC 75 0.31 25.9 83 17,650 10B9  BPEI25 MTC-Catechol 5 <0.0025 22.4 >8965 11,700 11 B10 BPEI25MTC-Catechol 12 <0.0025 30 >12006 14,080 12 B11 BPEI25 MTC-Catechol 200.0048 29.6 6171 20,880 Control BPEI1.8 0.5 122 244 1,800 13 B12 BPEI1.8MTC-IPMAN 4 0.9 124.1 137 3,088 14 B13 BPEI1.8 MTC-IPMAN 97.9 >1000 >126 4,698 15 B14 BPEI1.8 MTC-IPMAN 17 110.1 >1000 >9 7,274 16L1  LPEI25 MTC-IPMAN 8 1 122.3 122 13,526 17 L2  LPEI25 MTC-IPMAN 151.13 129.2 114 15,780 18 L3  LPEI25 MTC-IPMAN 26 I.4 523 37 19,322^(a)EC50 is the effective concentration at which the polymer protects50% of the cells from viral infection. A low EC50 value is desirable.^(b)CC50 is the cytotoxic polymer concentration, at which 50% of thecells are killed. A high CC50 value is desirable. ^(c)Selectivity isdefined as CC50/EC50. A high selectivity is desirable. ^(d)Obtained from¹H NMR.

The polymers inhibited DENV-2 replication in a dose-dependent mannerwith low EC50 values ranging from 0.01 to 50.5 mg/L. Non-modified BPEI25(control sample) was the most potent polymer against dengue viralinfection, having the lowest EC50 (0.01 mg/L). Non-modified BPEI25 wasalso the most cytotoxic, having a CC50 of 5.44 mg/L. Although mannosesubstitution decreased anti-viral capacity (i.e., increased EC50), thisapproach effectively mitigated PEI cytotoxicity (i.e., CC50 increasedwith increasing mannose modification). For example, CC50 increased from26.7 to higher than 1000 mg/L when the number of mannose groups wasincreased from 28 to 65 (B1-B3, respectively). Among all polymers, B3with 65 mannose residues had the highest selectivity index (SI, i.e.CC50/EC50) of 3333. A high selectivity is desirable.

The anti-viral activity of B3 against DENV-2 was further evaluated inclinically relevant human primary peripheral blood mononuclear cells(PBMCs, FIG. 3, graph) and macrophages (FIG. 4, graph). In FIG. 3, aftervirus infection, the peak shifts to a higher PE-A (phycoerythrin(PE)-conjugated anti-mouse IgG). The peaks for the samples obtained fromB3 treatment at 2 or 10 mg/L do not shift, but rather almost overlapwith the peak for the control sample without virus infection, indicatingthat B3 treatment effectively prevents human primary peripheral bloodmononuclear cells from DENV-2 infection. In FIG. 4, after virusinfection, the peak is shifted to a slightly higher PE-A. The peaks forthe samples obtained from B3 treatment at 2 or 10 mg/L do not shift, butrather almost overlap with the peak for the control sample without virusinfection, indicating that B3 treatment effectively prevents macrophagesfrom DENV-2 infection. These results show that B3 effectively preventedthe cells from DENV-2 infection. Both PBMCs and macrophages expressmannose receptor, which mediates DENV-2 infection. The mannose groups ofthe modified PEI polymers compete with DENV-2 for binding the mannosereceptor, thereby inhibiting the viral infection.

Broad-Spectrum Anti-Viral Activity

The anti-viral activity of mannose modified BPEI25 polymers B2 and B3was further evaluated against a broad spectrum of viruses includingother serotypes of dengue virus (DENV-1, 3 and 4), HSV-1, HSV-2, CHIKV,SARS Co-V, and EV 71. The results are listed in Table 5.

TABLE 5 Selectivity^(c) Virus CC50^(b) (CC50/ Name Type Family CellPolymer EC50^(a) (mg/L) (mg/L) EC50) DENV-1 RNA Flaviviridae LLC-MK2 B30.20 ± 0.17 >1000 >5000 DENV-2 RNA Flaviviridae LLC-MK2 B3 0.31 ±0.06 >1000 >3225

B3 was active against DENV-1, DENV-2, and DENV-4 with EC50 values of0.20, 0.32, and 0.31 mg/L, respectively. B3 had low activity againstDENV-3 with an EC50 value of 479 mg/L. However, B2, having less mannosesubstitution and higher charge, was active against DENV-3 with EC50 of0.80 mg/L. Notably, B3 effectively inhibited infections of respectivetarget cells with the DNA viruses HSV-1 and HSV-2, and the RNA virusesCHIKV, SARS Co-V, and EV 71 (non-enveloped). B3 was ineffective againstinfluenza infection, with EC50>1000 mg/L, whereas B2 effectivelyprevented infection of influenza virus, with a low EC50 value of <0.012mg/L. These findings demonstrate broad-spectrum anti-viral activity ofthe polymers. Importantly, there was no significant cytotoxicity atconcentrations where the polymer prevented 100% cells from infection.

Inhibition of Viral Infection in Cells Expressed with TIM-1 and TIM-3Receptors

TIM receptors facilitate virus entry by directly interacting withphosphatidylserine (PS) on the viral envelope. Establishment of the 293Tcells stably expressing the TIM-1 or TIM-3 protein, lentiviral vectorswere generated as described by Tahara-Hanaoka S, et. al. “Lentiviralvector-mediated transduction of murine CD34-hematopoietic stem cells”,Experimental Hematology, (2002), 30, pages 11-17). 293T cells weretransfected with pseudoviruses carrying the desired ORF (open readingframe, a reading frame that contains no stop codons). Cells with theexpression of TIM-1 or TIM-3 were selected by blasticidin (InvivoGen,Toulouse, France). 293T cells stably express TIM-1 or TIM-3 due tointegration of TIM-1 or TIM-3 expression genes.

Parental (with empty vector), TIM-1, and TIM-3 expressing 293T cellswere challenged with CHIKV at multiplicity of infection (M.O.I) 0.1along with B3 (50 mg/L) added at the same time. Supernatants werecollected 48 hours post-infection. Virus titers were determined byplaque assay and expressed as average plaque forming unit per ml(pfu/mL) of three replicates±SD.

Expression of TIM-1 and TIM-3 receptors in 293T cells significantlyenhanced CHIK infection (FIG. 5, bar graph, TIM1-293T and TIM3-293Tversus empty vector-293T cells). FIG. 6 is a bar graph showing theeffect of B3 in preventing CHIKV infection of the empty vector 293Tcells (i.e., that do not express the TIM-1 or TIM-3 receptor), where theEC50 was 2.6 mg/L. FIG. 7 is a bar graph showing the effect of B3 inpreventing CHIKV infection in the TIM1-293T cells, where the EC50 was2.9 mg/L. FIG. 8 is a bar graph showing the effect of B3 in preventingCHIKV infection in the TIM3-293T cells, where the EC50 was 2.7 mg/L. Theselectivity (CC50/EC50) towards preventing CHIKV infection in TIM-1 andTIM-3 expressing cells was high (>345 and >370, respectively).

B3 also effectively inhibited DENV-2 infection of A549 cells thatnaturally express the TIM-1 receptor (FIG. 9, bar graph). In thisinstance the EC50 was 6.8 mg/L, CC50 was >1000 mg/L, and the selectivityindex was >147, measured by plaque reduction assay. These findingssuggest that the polymer is capable of inhibiting the phosphatidylserine(PS)/TIM receptor binding possibly by hydrogen-bonding interactionsbetween polymer and TIM-1/TIM-3 receptors (see below FIGS. 34-37) and/orelectrostatic interaction between the cationic charges on the polymerand the negative charges on the PS, hence preventing viral infection ofcells with TIM-1 or TIM-3 receptor expression.

Anti-Viral Mechanism Inhibition of Viral Entry

Viral particles infect cells by specific interactions of their surfaceproteins with receptors including proteins, mannose receptors (alsotargeted by immune cells), heparan sulfate proteoglycans (targeted byDENV, HSV, EV 71, SARS-CoV) and sialic acid (influenza virus, EV 71) onthe cell membrane, followed by endocytosis internalization. Virusesspread viral genome and infection from cell to cell. To study if thepolymer exerts its anti-viral effect at an early or late stage of viruslife cycle, the effect of the macromolecule on the replication of DENV-2subgenomic replicon, encoding only non-structural viral proteins, wasstudied in luciferase-replicon transfected A459 cells.

Replicon luciferase assay. A549 cells (human male lung carcinoma)containing a luciferase-reporting replicon of DENV-2 were seeded at acell density of 25×10⁴ cells/well in 6-well plates. The cells weretreated with 50 mg/L of B3 polymer c, 100 mg/L of NITD008, or mediumwith DMSO. NITD008 was not water soluble, and a small amount of DMSO(dimethylsulfoxide) was used to promote its dissolution in the cellculture medium. After incubation for 48 hours, luciferase activity wasmeasured using the Renilla luciferase assay system (Promega, Madison,Wis.). Results were normalized by protein quantity.

FIG. 10 is a bar graph comparing the luciferase activity of the A459cells without B3 (labeled DMSO), with B3, and a with a potent anti-viraladenosine nucleoside analogue NITD008,(2R,3R,4R,5R)-2-(4-aminopyrrolo[2,3-d]pyrimidin-7-yl)-3-ethynyl-5-(hydroxymethyl)oxolane-3,4-diol.The results show that NITD008 was effective and B3 was not effective ininhibiting replication of the DENV-2 subgenomic replicon. This findingdemonstrated that the anti-viral polymer did not function at a latestage of the DENV-2 life cycle.

To examine if the polymer blocked the initial attachment step in theLLC-MK2 cells or a downstream event in the viral entry process, B3 wasadded together with DENV-2 to the cells for 90 minutes at 4° C. Unboundpolymer molecules were then removed by PBS wash (3 times) before thecells were incubated for 5 days at 37° C. The B3 polymer inhibitedDENV-2 infection completely at this time of addition (−1.5 hours). Othertimes of addition were evaluated. FIG. 11 is set of graphs showing theeffect of time of addition of B3 (and heparin) on the inhibition ofDENV-2 in LLC-MK2 cells. The top graph shows the time of addition of B3and heparin. The bottom graph depicts the % inhibition obtained for eachtime of addition. Only at time −1.5 hours were the virus and polymer B3(or heparin) added together to the cells. At all other times, the virusand cells were incubated initially at 4° C. without the polymer B3 orheparin, followed by warming to 37° C., followed by addition of B3 orheparin at the indicated times. The results show that the viralinfection was effectively prevented when the polymer was added to thecells just after the cells and virus were incubated at 4° C. for 90minutes and warmed to a 37° C. (corresponding to Time=0 hours). However,when the polymer was added to the cells after the cells and DENV-2 wereincubated for 1 hour at 37° C., inhibition was significantly reduced. Noconsiderable inhibition was observed when the polymer was introducedafter the cells were infected with the virus for 2-5 hours at 37° C.These results demonstrated that the polymer was effective in preventingviral infection when added during the viral attachment step or earlypost-attachment step, confirming the point of action at DENVentry/membrane fusion.

To further understand the anti-viral mechanism, DENV-2 was incubatedwith 50 mg/L B3 for one hour at 4° C. for binding before performing aplaque assay to measure virus titers. Virus binding with the polymerlowered virus titers by more than 40%, indicating that the polymer boundthe virus, and prevented infection (FIG. 12, bar graph). In the cellculture medium (pH 7.4), the majority of primary and secondary aminesare protonated, making the polymer highly charged.

In addition to the specific viral protein/polymer interaction, thecationic charges of the polymer might interact with the anionic chargeson the envelope of virus through electrostatic interaction. This mightmask the virus, preventing the cells from viral infection.

On the other hand, at 50 mg/L, the polymer B3 yielded completeinhibition of viral infection when it was added to the cells togetherwith the virus. The incomplete inhibition of virus titers after polymerbinding at the same concentration implied that there were other factorssuch as binding between the polymer and anionic components on the cellmembrane (anionic heparin sulfate proteoglycans) and neutralization ofthe endosomal pH, which contributed to the inhibition of viralinfection. Although all primary amine groups were substituted by mannosegroups, B3 carries cationic charges at pH 7.4 as the majority ofsecondary amine groups (pKa: 8.6) and ˜50% tertiary amines (pKa: 7.5)can be protonated. Indeed, the pretreatment of the cells using 50 mg/LB3 at 2 hours or even 15 minutes effectively prevented DENV-2 infection(FIG. 13, bar graph). The EC50 value of B3 against DENV-2 infection was6.0 mg/L when the cells were pre-incubated with B3 for one hour beforethe virus was added. This value was higher than when the polymer, celland virus were incubated at the same time (EC50: 0.30 mg/L, Table 4).The pretreatment of Vero and RD cells was also highly effective againstCHIKV, HSV-1 and EV 71 at EC50 values of 23.5, 1.8 and 0.80 mg/L,respectively. These findings indicate that binding of B3 onto the cellmembranes was an important factor in blocking viral entry.

In addition, the unprotonated secondary and tertiary amines of PEIpolymers are capable of being protonated in the endosomal environment(pH 5.0-6.5), thus neutralizing the endosomal pH. Neutralization of theendosomal pH is known to inhibit pH-dependent viral infections such asDENY, CHIKV, influenza virus, HSV, and EV 71. To prove that the polymeris able to inhibit low pH-induced virus-cell membrane fusion, preventionof low pH-induced virus-infected cell fusion was investigated.Virus-infected cell fusion was reported to be due to fusogenic viralproteins that are expressed on the cell surface after infection. C6/36Aedes albopictus cells were incubated with DENV-2 for 90 minutes at 4°C. with and without B3 (50 mg/L), followed by incubation at 28° C. for 2days to allow infection and for another 2 days after acidification to pH5.0 with MES (2-(N-morpholino)ethanesulfonic acid). FIG. 14 is a set ofphotomicrographs and corresponding procedure diagrams showing the effectof B3 and heparin on virus-infected cell fusion of the C6/36 cells. Theanti-viral agent was added at 4° C. (images labeled “4° C.+”) or at 28°C. (images labeled “4° C.-”). The samples labeled “Medium” containedonly cells and virus (no anti-viral agent). The samples labeled “Mock”contained only cells (no virus or anti-viral agent). No fused cells werefound in the samples containing B3. Unlike the control group without anytreatment, no fused cells were found in the samples containing B3. Thepolymer inhibited syncytia formation even when it was added at the pointof viral infection (i.e., incubation at 28° C.), suggesting that thepolymer was indeed capable of preventing low pH-induced virus-cellmembrane fusion and viral infection.

Summarizing, in general with the treatment of DENY, cationic polymerswith higher levels of mannose had lower capacity to neutralize theendosomal pH and less cationic charge, which diminished anti-viralactivity. Without being bound by theory, polymer-virus binding,polymer-cell membrane interaction and neutralization of the endosomal pHacting together may explain prevention of viral infection.

Prevention of Drug Resistance.

Although there are anti-viral drugs available for some viral infectionssuch as influenza, viruses are able to develop drug resistance viamutations. For example, adamantane resistance (e.g., resistance to M2protein inhibitors) has been frequently found in circulating influenzastrains since 2003. Oseltamivir and zanamivir (neuraminidaseinhibitors), which are effective against adamantane-resistant influenzaviruses and recommended by the Center for Disease Control, USA (CDC) fortreatment and prophylaxis of influenza infections, have also seenreduced effectiveness in a small number of influenza viruses. Resistanceis associated with a single amino acid change in M2 or neuraminidaseprotein. In order to investigate if the antiviral activity mediated bythe polymers through multiple mechanisms adequately prevents drugresistance development, DENV-2 exposed to a sub-lethal dose of B3 (0.31mg/L) was passaged and used to determine EC50 values up to 5 passages.EC50 values remained similar (0.31-0.35 mg/L). In addition, afterpassage 5, the virus was treated with the polymer at 100 mg/L, whichcompletely inhibited DENV-2 infection. These results indicate thatrepeated treatment with B3 did not mediate resistance in DENV-2.

In Vivo Toxicity

To demonstrate the potential of the cationic polyamines for in vivoapplications, the in vivo toxicity levels of B2 and B3 wereinvestigated. The LD50 values (lethal dose at which half the mice arekilled in a two week period) via intravenous injection of B2 and B3 weredetermined to be 313 mg/kg and 463 mg/kg, respectively, indicating thatthe cationic polyamines have low toxicity.

To evaluate the acute toxicity of B3 towards major organs (the liver andkidney) and the blood, alanine transaminase (ALT), aspartatetransaminase (AST), total bilirubin (TBIL), creatinine, urea nitrogen,sodium ion, and potassium ions levels were measured in blood samplestaken from B3-treated mice 48 hours after intravenous injection. Table 6lists the results. The data are expressed as mean+standard deviation,based on values obtained from 10 mice (n=10). Statistical analysis wasperformed using Student's t-test. Differences are consideredstatistically significant with probability P<0.05. The followingabbreviations are used: ALT=alanine transaminase; AST=aspartatetransaminase; TBIL=total bilirubin; Units=international units.

TABLE 6 Urea ALT AST Creatinine nitrogen K⁺ Na⁺ Treatment (Units/L)(Units/L) TBIL (micromol/L) (mmol/L) (mmol/L) (mmol/L) w/o 21.0 ± 4.958.2 ± 13.2 2.0 ± 0.0 10.8 ± 1.7 6.9 ± 0.9 4.7 ± 0.3 147.7 ± 1.9treatment (n = 10) (n = 10) (n = 10) (n = 10) (n = 10) (n = 10) (n = 10)48 hours 23.3 ± 3.6 65.0 ± 23.8 2.1 ± 0.3 11.4 ± 1.0 6.0 ± 0.4 4.8 ± 0.2143.9 ± 2.4 post- (n = 10) (n = 10) (n = 10) (n = 10) (n = 10) (n = 10)(n = 10) treatment p = 0.40 > 0.05 p = 0.21 > 0.05 p = 0.34 > 0.05 p =1.0 > 0.05 p = 0.55 > 0.05 p = 0.47 > 0.05 p = 0.43 > 0.05 14 days 21.9± 1.8 64.8 ± 20.4 2.0 ± 0.0 10.7 ± 0.8 7.5 ± 0.6 4.6 ± 0.3 145.5 ± 1.1post- (n = 10) (n = 10) (n = 10) (n = 10) (n = 10) (n = 10) (n = 10)treatment p = 0.60 > 0.05 p = 0.45 > 0.05 p = 1.0 > 0.05 p = 1.0 > 0.05p = 0.44 > 0.05 p = 0.27 > 0.05 p = 0.31 > 0.05

There was no significant difference in any of the measured parametersbetween the control group and the group receiving intravenous injectionof B3 at a concentration well above its effective concentration (dose:60 mg/kg; estimated concentration in the blood: 1200 mg/L, assuming thatthe blood volume of the mouse is ˜1 mL), indicating that the polymertreatment did not lead to any acute liver or kidney damage, norinterfere with the electrolyte balance of the blood. In addition, evenat 14 days post-injection, the liver and kidney functions, potassium andsodium ion concentrations remained unchanged as compared to the control.Moreover, the polymer treatment did not induce any abnormal color changein the serum or urine samples, or cause lethality in mice. These resultsprove that the polymer treatment was not toxic in mice during the periodof testing.

Blind Docking Study of Modified and Unmodified PEI with Viral Proteins

Blind docking study provides insight into binding interactions betweenpolymer and viral proteins.

The crystal structure of DENV-2 E glycoprotein was retrieved from theProtein Data Bank (PDB ID: 1OKE). The crystal structure details Eprotein in its dimeric pre-fusion conformation. The crystal structuresof DENV-3 (PDB ID: 1UZG), HSV-1 (PDB ID: 1JMA), HSV-2 (PDB ID: 4MYW),influenza virus (PDB ID: 4KVN) and TIM1 (PDB ID: 2OR8) were alsoretrieved from PDB. The amino acid sequence for CHIKV (ID: ACT35081.1)and EV 71 (ID: ACS12925) were downloaded from National Center forBiotechnology Information (NCBI, USA) and the protein structures weremodelled using the I-Tasser online server. The two dimensional structureof a model macromolecule of branched PEI (FIG. 15) was built usingMarvin Sketch software and converted into three dimensional structureusing OpenBabel software. The model branched PEI and a model cationicpolyamines B3 and B2 that were used in the docking study were notintended to represent the complete structures of the branched PEI and B3materials of the above examples. The model B3 material had 3 mannosegroups, and the model B2 material had 2 mannose groups. MVD (MolegroVirtual Docker) was used to identify the potential binding sites of B3and non-modified branched PEI in the viral proteins in order to performthe molecular docking analysis. A cavity detection algorithm was used todetect cavities in order to narrow down the binding sites. Thestructures of protein and ligand (one unit of macromolecule of modelbranched PEI or model cationic polyamine B3) were prepared by MVD.Bonds, hydrogens, and bond orders were assigned if missing. The chargesand flexible torsions in the ligand were assigned. The grid-basedMolDock scoring function was used to define the energy terms to rank thepotential binding sites. Grids of 30 Å radius were used as search spaceon the proteins. The MolDock Simplex evolution algorithm was chosen witha population size of 100. The simplex minimization procedure wasperformed and the energy threshold was set to 100 for pose generation.

The protein-polymer interaction was analyzed through the flexible liganddocking study. Interaction between a ligand and a protein is defined asspecific when the ligand binds to the protein at a specific binding sitewith the least energy, while interaction is defined as non-specific whenthe ligand binds to the protein at various sites in the same range ofenergy. Five binding poses in each grid were obtained from the flexibledocking, and by ranking Moldock and rerank scores of the poses, the onewith the least score was considered to be the best docking pose. Thebest pose is predicted to be present in one of the five cavitiesdetected by the MVD software.

The DENV-2 E protein (envelope protein) has 5 cavities. The MVD dockingstudies of the DENV-2 E protein were performed utilizing 4 grids. FIG.16 is an MVD 3-dimensional computer drawing of the DENV-2 E protein, inwhich the highlighted speckled areas represent 4 poses of the modelbranched PEI bound with equal binding energy in the 4 grids. Thehydrogen bonds were estimated.

The specific binding site of the model cationic polyamine B3 to theDENV-2 E protein was predicted to be at the interface of the domain IIand domain III of the E protein dimer and near the fusion loop of the Eprotein monomer. FIG. 17 is a computer drawing showing the 8 amino acidgroups of the DENV-2 E protein (envelope protein) that form hydrogenbonds with a model cationic polyamine B3 structure: Thr 70, Thr 115, Asp154, Gln 248, Gly 266, Ala 267, Thr 268 and Leu 277. FIG. 18 is a3-dimensional computer drawing of the most favored binding of the modelcationic polyamine B3 to the DENV-2 E protein. The binding site is alsolocated in a pocket above the flexible ‘kl’ loop lining the hydrophobiccavity called the BOG binding pocket by previous studies.

FIG. 19 is a computer drawing using MVD software showing the 7 aminoacid groups of EV 71 VP1 protein that form hydrogen bonds with the modelcationic polyamine B3: Gln 269, Arg 267, Glu 124, Asn 228, Ser 275, Ala224, and Gly 223.

FIG. 20 is a 3-dimensional computer drawing using MVD software showingthe most favored binding of the model cationic polyamine B3 with the EV71 VP1 protein.

FIG. 21 is a computer drawing using MVD software showing the 7 aminoacid groups of HSV-1 GD protein that form hydrogen bonds with the modelcationic polyamine B3: Asp 13, Asn 15, Arg 18, Leu 22, Val 24, Gln 27,Ser 8.

FIG. 22 is a 3-dimensional computer drawing using MVD software showingthe most favored binding interaction of the model cationic polyamine B3with the HSV-1 GD protein.

FIG. 23 is a computer drawing using MVD software showing the 7 aminoacid residues of DENV-3 E protein that form hydrogen bonds with themodel cationic polyamine B3: Thr 155(B), Lys 47(B), Thr 274(B), Ser271(B), Asn 8(B), and Asp 98(A), His 27(B),

The DENV-3 E protein has 5 cavities detected by MVD software. FIG. 24 isa 3-dimensional computer drawing using MVD software of 5 cavities in theDENV-3 E protein.

FIG. 25 is a 3-dimensional computer drawing using MVD software showingthe most favored binding interaction of the model cationic polyamine B3with the DENV-3 E protein.

FIG. 26 is a computer drawing using MVD software showing the 7 aminoacid residues of the CHIKV E1 protein that interact by hydrogen bondingwith the model cationic polyamine B3: Gln 373, Gln 368, Thr 17, Gly 12,Glu 32, Thr 338, and His 394.

FIG. 27 is a 3-dimensional computer drawing using MVD software of themost favored binding interaction of the model cationic polyamine B3 withthe CHIKV E1 protein.

FIG. 28 is a computer drawing using MVD software showing the 4 aminoacid residues of influenza virus HA protein that form hydrogen bondswith the model cationic polyamine B3: Arg 285, Ser 282, Ser 130, and Phe415.

FIG. 29 is a 3-dimensional computer drawing using MVD software of the 4cavities in the HA protein.

FIG. 30 is a 3-dimensional computer drawing using MVD software showingthe most favored binding of the model cationic polyamine B3 to the HAprotein.

FIG. 31 is a computer drawing using MVD software showing the 9 aminoacid residues of HSV-2 GD protein that form hydrogen bonds with themodel cationic polyamine B3: Asp 139, Arg 222, Ser 140, Asp 26, Asn 227,Thr 230, Lys 237, Val 24, and Gln 27.

FIG. 32 is a 3-dimensional computer drawing using MVD software of 4cavities in the GD protein.

FIG. 33 is a 3-dimensional computer drawing using MVD software showingthe most favored binding interaction of the model cationic polyamine B3to the GD protein.

FIG. 34 is a computer drawing using MVD software showing the 8 aminoacid residues of the TIM-1 protein that form hydrogen bonds with themodel cationic polyamine B3: Lys 102(B), Ser 3(B), Thr 20(A), Thr 20(B),Ser 22(A), Gln 101 (A), Asp 100(A), and Glu 6(B).

FIG. 35 is a 3-dimensional computer drawing using MVD software showingthe most favored binding interaction of the model cationic polyamine B3to the TIM-1 protein.

FIG. 36 is a computer drawing using MVD software showing the 5 aminoacid residues of TIM-3 protein that form hydrogen bonds with the modelcationic polyamine B3: Glu 106(A), Cys 39(A), Lys 103(A), Ser 20(A), andTyr 7(A).

FIG. 37 is a 3-dimensional computer drawing using MVD software showingthe most favored binding of the model cationic polyamine B3 to TIM-3.

FIG. 38 is a computer drawing using MVD software showing the 3 aminoacid residues of the DENV-3 E protein that form hydrogen bonds with themodel cationic polyamine B3 structure: Glu 13(A), Ala 35(A), and Phe335(A).

FIG. 39 is a 3-dimensional computer drawing using MVD software showingthe most favored binding interaction of the model cationic polyamine B3to the DENV-3 E protein.

FIG. 40 is a computer drawing using MVD software showing the 5 aminoacid residues of the Influenza HA protein that form hydrogen bonds withthe model cationic polyamine B2: Arg 285, Glu 430, Ser 282, Ile 283, andAsp 287.

FIG. 41 is a 3-dimensional computer drawing using MVD software showingthe most favored binding of the model cationic polyamine B2 to theInfluenza HA protein.

In addition, docking results showed that the non-modified PEI-viralprotein interaction was non-specific.

Table 7 summarizes the Moldock score, Rerank score, and calculatednumber of interacting amino acids forming hydrogen bonds with modelcationic polyamine B3 with various viral proteins, obtained using theMVD software.

TABLE 7 No. of Moldock Rerank interacting Virus Type Protein InteractionScore Score amino acids DENV-2 RNA E Specific −192.45 −95.43 8 DENV-3RNA E Specific −140.82 −94.98 7 CHIKV RNA E1 Specific −144.06 −59.43 7EV 71 RNA VP1 Specific −146.60 −60.07 7 Influenza RNA HA Specific −97.30−31.09 4 virus (A/H3N2) HSV-1 DNA GB Specific −56.88 104.77 7 HSV-2 DNAGB Specific −95.34 −26.45 9 TIM-1 Specific −158.36 −93.36 8 TIM-3Specific −117.11 18.62 5

Table 8 summarizes the Moldock score, Rerank score, and calculatednumber of interacting amino acids forming hydrogen bonds by modelcationic polyamine B2 with DENV-3 E protein and Influenza HA proteinusing MVD software.

TABLE 8 No. of Moldock Rerank interacting Virus Type Protein InteractionScore Score amino acids DENV-3 RNA E Specific −152.30 −97.81 3 InfluenzaRNA HA Specific −148.77 −75.59 5 virus (A/H3N2)

CONCLUSION

Linear and branched PEI were modified in a rapid and facile nucleophilicaddition reaction with a mannose-functionalized cyclic carbonatemonomer. The resulting cationic polyamines display strong anti-viralactivity, negligible toxicity and high selectivity towards virusparticles over mammalian cells. The above data shows that anti-viralactivity decreased (EC50 increased) with increasing mannose content ofthe modified BPEI25 (Table 5, B1-B6). Offsetting this trend in EC50 wasa more rapidly decreasing cytotoxicity (increasing CC50) resulting inincreasing selectivity (increasing CC50) with increasing mannose content(Table 5, B1-B6). The incorporation of mannose residues lowers PEItoxicity and allows targeting of the mannose receptor on the immunecells. The mannose-modified PEI specifically binds to viral surfaceproteins. The modified polymers have broad-spectrum anti-viral activity,effective against DNA, RNA, enveloped and non-enveloped viralinfections, including DENY, HSV-1, HSV-2, CHIKV, SARS Co-V and EV 71.The cationic polyamines prevent viral infection by binding with viraland cell surfaces, inhibiting virus entry/membrane fusion andneutralizing the endosomal pH (mitigating membrane fusion). The cationicpolyamines are also effective against viral infection of cellsexpressing TIM-1 or TIM-3. Importantly, by targeting both viral proteinsand host-virus interactions, the antiviral polymers can mitigate drugresistance. Mannose-carbamate modified PEI has broad-spectrum anti-viralactivity and no in vivo toxicity at its effective concentration,resulting in great potential for the prevention and treatment of avariety of viral infections.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. When a range is used to express apossible value using two numerical limits X and Y (e.g., a concentrationof X ppm to Y ppm), unless otherwise stated the value can be X, Y, orany number between X and Y.

The description of the present invention has been presented for purposesof illustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiments were chosen and described in order to best explain theprinciples of the invention and their practical application, and toenable others of ordinary skill in the art to understand the invention.

What is claimed is:
 1. A method, comprising: treating a virus with acationic polyamine, the virus comprising DNA and/or RNA, the viruscapable of causing a viral disease in mammals, thereby forming a treatedvirus comprising the cationic polyamine bound by non-covalentinteractions to the virus; wherein: i) the treated virus is less capableof entering a living mammalian cell and/or undergoing replication withina living mammalian cell compared to the virus before said treating, ii)the cationic polyamine comprises: a plurality of non-charged N-acylatedethylenimine units of formula (1):

wherein each K′ comprises at least one carbon and at least one alcoholhydroxyl group, and a plurality of positive-charged secondaryethylenimine units of formula (3a):

wherein the starred bond of the nitrogen is linked to a carbon and X^(⊖)is a negative-charged counterion bound by non-covalent association withthe positive charged nitrogen, and iii) the cationic polyamine comprisesthe N-acylated ethylenimine units and the secondary ethylenimine unitsarranged in a random distribution and linked covalently head-to-tail,wherein nitrogen 1 of a given ethylenimine unit is linked to carbon 3 ofa different ethylenimine unit.
 2. The method of claim 1, wherein each K′comprises a monovalent monosaccharide moiety.
 3. The method of claim 2,wherein the monosaccharide moiety is selected from the group consistingof glucosyl groups, galactosyl groups, and mannosyl groups.
 4. Themethod of claim 2, wherein the monosaccharide moiety is selected fromthe group consisting of


5. The method of claim 1, wherein each K′ comprises a catechol group. 6.The method of claim 1, wherein each *—C(═O)K′ of the cationic polyamineis an independent monovalent radical selected from the group consistingof:


7. The method of claim 1, wherein the cationic polyamine has one polymerbranch consisting essentially of the N-acylated ethylenimine units, thesecondary ethylenimine units, and polymer chain end groups.
 8. Themethod of claim 1, wherein the cationic polyamine further comprises anoxidized ethylenimine unit having the structure:


9. The method of claim 1, wherein the virus is a dengue virus.
 10. Themethod of claim 1, wherein the cationic polyamine has a plurality ofpolymer branches comprising the N-acylated ethylenimine units, thesecondary ethylenimine units, and tertiary ethylenimine unit having thestructure

wherein X^(⊖) is a negative-charged counterion bound by non-covalentassociation with the positive charged nitrogen.
 11. The method of claim10, wherein the cationic polyamine is formed in a process comprisingtreating a branched polyethylenimine with an acylating agent comprisingK′ and/or a protected form of K′.
 12. The method of claim 11, whereinthe branched polyethylenimine has a number average molecular weight (Mn)greater than
 1000. 13. A method, comprising: treating a living mammaliancell with a cationic polyamine, the cell comprising a cell membrane,thereby forming a treated cell comprising the cationic polyamine boundby non-covalent interactions to the cell membrane; wherein: i) thetreated cell has more resistance to a virus entering the treated celland/or replicating within the treated cell compared to the cell beforesaid treating, the virus comprising DNA and/or RNA, the virus capable ofcausing a viral disease in mammals, ii) the cationic polyaminecomprises: a plurality of non-charged N-acylated ethylenimine units offormula (1):

wherein each K′ comprises at least one carbon and at least one alcoholhydroxyl group, and a plurality of positive-charged secondaryethylenimine units of formula (3a):

wherein the starred bond of the nitrogen is linked to a carbon, andX^(⊖) is a negative-charged counterion bound by non-covalent associationwith the positive charged nitrogen, and iii) the cationic polyaminecomprises the N-acylated ethylenimine units and the secondaryethylenimine units arranged in a random distribution and linkedcovalently head-to-tail, wherein nitrogen 1 of a given ethylenimine unitis linked to carbon 3 of a different ethylenimine unit.
 14. The methodof claim 13, wherein the virus is selected from the group consisting ofdengue fever viruses, SARS corona viruses, Chikungunya viruses,enteroviruses, influenza viruses, herpes simplex viruses, andcombinations thereof.
 15. The method of claim 13, wherein the cationicpolyamine inhibits entry of the virus into the mammalian cell bydisrupting endosomal release of the virus.
 16. The method of claim 13,wherein the mammalian cell is selected from the group consisting ofblood cells, liver cells, nasal cells, lung cells, and cervical cells.17. A method, comprising: administering to a patient infected with avirus a therapeutically effective amount of a cationic polyamine,thereby inhibiting and/or preventing replication of the virus, the viruscomprising DNA and/or RNA, the virus capable of causing a viral diseasein mammals, the cationic polyamine bound by non-covalent interactions tothe virus; wherein: i) the cationic polyamine comprises: a plurality ofnon-charged N-acylated ethylenimine units of formula (1):

wherein each K′ comprises at least one carbon and at least one alcoholhydroxyl group, and a plurality of positive-charged secondaryethylenimine units of formula (3a):

wherein the starred bond of the nitrogen is linked to a carbon, andX^(⊖) is a negative-charged counterion bound by non-covalent associationwith the positive charged nitrogen, and ii) the cationic polyaminecomprises the N-acylated ethylenimine units and the secondaryethylenimine units arranged in a random distribution and linkedcovalently head-to-tail, wherein nitrogen 1 of a given ethylenimine unitis linked to carbon 3 of a different ethylenimine unit.
 18. The methodof claim 17, wherein the cationic polyamine is administered as anaqueous mixture.
 19. The method of claim 18, wherein the aqueous mixtureis administered by injection.
 20. The method of claim 17, wherein thecationic polyamine binds non-covalently to the virus, thereby impedingentry of the virus into cells of the patient.
 21. The method of claim17, wherein the cationic polyamine binds non-covalently to cells of thepatient, thereby impeding entry of the virus into the cells of thepatient.
 22. The method of claim 17, wherein the cationic polyamine isnon-cytotoxic at the therapeutically effective dose.